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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
linux-next for a couple of months without, to my knowledge, any
negative reports (or any positive ones, come to that).
- Also the Maple Tree from Liam Howlett. An overlapping range-based
tree for vmas. It it apparently slightly more efficient in its own
right, but is mainly targeted at enabling work to reduce mmap_lock
contention.
Liam has identified a number of other tree users in the kernel which
could be beneficially onverted to mapletrees.
Yu Zhao has identified a hard-to-hit but "easy to fix" lockdep splat
at [1]. This has yet to be addressed due to Liam's unfortunately
timed vacation. He is now back and we'll get this fixed up.
- Dmitry Vyukov introduces KMSAN: the Kernel Memory Sanitizer. It uses
clang-generated instrumentation to detect used-unintialized bugs down
to the single bit level.
KMSAN keeps finding bugs. New ones, as well as the legacy ones.
- Yang Shi adds a userspace mechanism (madvise) to induce a collapse of
memory into THPs.
- Zach O'Keefe has expanded Yang Shi's madvise(MADV_COLLAPSE) to
support file/shmem-backed pages.
- userfaultfd updates from Axel Rasmussen
- zsmalloc cleanups from Alexey Romanov
- cleanups from Miaohe Lin: vmscan, hugetlb_cgroup, hugetlb and
memory-failure
- Huang Ying adds enhancements to NUMA balancing memory tiering mode's
page promotion, with a new way of detecting hot pages.
- memcg updates from Shakeel Butt: charging optimizations and reduced
memory consumption.
- memcg cleanups from Kairui Song.
- memcg fixes and cleanups from Johannes Weiner.
- Vishal Moola provides more folio conversions
- Zhang Yi removed ll_rw_block() :(
- migration enhancements from Peter Xu
- migration error-path bugfixes from Huang Ying
- Aneesh Kumar added ability for a device driver to alter the memory
tiering promotion paths. For optimizations by PMEM drivers, DRM
drivers, etc.
- vma merging improvements from Jakub Matěn.
- NUMA hinting cleanups from David Hildenbrand.
- xu xin added aditional userspace visibility into KSM merging
activity.
- THP & KSM code consolidation from Qi Zheng.
- more folio work from Matthew Wilcox.
- KASAN updates from Andrey Konovalov.
- DAMON cleanups from Kaixu Xia.
- DAMON work from SeongJae Park: fixes, cleanups.
- hugetlb sysfs cleanups from Muchun Song.
- Mike Kravetz fixes locking issues in hugetlbfs and in hugetlb core.
Link: https://lkml.kernel.org/r/CAOUHufZabH85CeUN-MEMgL8gJGzJEWUrkiM58JkTbBhh-jew0Q@mail.gmail.com [1]
* tag 'mm-stable-2022-10-08' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (555 commits)
hugetlb: allocate vma lock for all sharable vmas
hugetlb: take hugetlb vma_lock when clearing vma_lock->vma pointer
hugetlb: fix vma lock handling during split vma and range unmapping
mglru: mm/vmscan.c: fix imprecise comments
mm/mglru: don't sync disk for each aging cycle
mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol
mm: memcontrol: use do_memsw_account() in a few more places
mm: memcontrol: deprecate swapaccounting=0 mode
mm: memcontrol: don't allocate cgroup swap arrays when memcg is disabled
mm/secretmem: remove reduntant return value
mm/hugetlb: add available_huge_pages() func
mm: remove unused inline functions from include/linux/mm_inline.h
selftests/vm: add selftest for MADV_COLLAPSE of uffd-minor memory
selftests/vm: add file/shmem MADV_COLLAPSE selftest for cleared pmd
selftests/vm: add thp collapse shmem testing
selftests/vm: add thp collapse file and tmpfs testing
selftests/vm: modularize thp collapse memory operations
selftests/vm: dedup THP helpers
mm/khugepaged: add tracepoint to hpage_collapse_scan_file()
mm/madvise: add file and shmem support to MADV_COLLAPSE
...
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Define ELFOSABI_XTENSA_FDPIC and use it as an OSABI tag in the ELF
header to distinguish FDPIC ELF files from regular ELF files.
Define ELF_FDPIC_PLAT_INIT and put executable map, interpreter map and
executable dynamic section addresses into registers a4..a6.
Update start_thread macro to preserve register values in the current
register window.
Add definitions for PTRACE_GETFDPIC, PTRACE_GETFDPIC_EXEC and
PTRACE_GETFDPIC_INTERP.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
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This idea was introduced by David Rientjes[1].
Introduce a new madvise mode, MADV_COLLAPSE, that allows users to request
a synchronous collapse of memory at their own expense.
The benefits of this approach are:
* CPU is charged to the process that wants to spend the cycles for the
THP
* Avoid unpredictable timing of khugepaged collapse
Semantics
This call is independent of the system-wide THP sysfs settings, but will
fail for memory marked VM_NOHUGEPAGE. If the ranges provided span
multiple VMAs, the semantics of the collapse over each VMA is independent
from the others. This implies a hugepage cannot cross a VMA boundary. If
collapse of a given hugepage-aligned/sized region fails, the operation may
continue to attempt collapsing the remainder of memory specified.
The memory ranges provided must be page-aligned, but are not required to
be hugepage-aligned. If the memory ranges are not hugepage-aligned, the
start/end of the range will be clamped to the first/last hugepage-aligned
address covered by said range. The memory ranges must span at least one
hugepage-sized region.
All non-resident pages covered by the range will first be
swapped/faulted-in, before being internally copied onto a freshly
allocated hugepage. Unmapped pages will have their data directly
initialized to 0 in the new hugepage. However, for every eligible
hugepage aligned/sized region to-be collapsed, at least one page must
currently be backed by memory (a PMD covering the address range must
already exist).
Allocation for the new hugepage may enter direct reclaim and/or
compaction, regardless of VMA flags. When the system has multiple NUMA
nodes, the hugepage will be allocated from the node providing the most
native pages. This operation operates on the current state of the
specified process and makes no persistent changes or guarantees on how
pages will be mapped, constructed, or faulted in the future
Return Value
If all hugepage-sized/aligned regions covered by the provided range were
either successfully collapsed, or were already PMD-mapped THPs, this
operation will be deemed successful. On success, process_madvise(2)
returns the number of bytes advised, and madvise(2) returns 0. Else, -1
is returned and errno is set to indicate the error for the most-recently
attempted hugepage collapse. Note that many failures might have occurred,
since the operation may continue to collapse in the event a single
hugepage-sized/aligned region fails.
ENOMEM Memory allocation failed or VMA not found
EBUSY Memcg charging failed
EAGAIN Required resource temporarily unavailable. Try again
might succeed.
EINVAL Other error: No PMD found, subpage doesn't have Present
bit set, "Special" page no backed by struct page, VMA
incorrectly sized, address not page-aligned, ...
Most notable here is ENOMEM and EBUSY (new to madvise) which are intended
to provide the caller with actionable feedback so they may take an
appropriate fallback measure.
Use Cases
An immediate user of this new functionality are malloc() implementations
that manage memory in hugepage-sized chunks, but sometimes subrelease
memory back to the system in native-sized chunks via MADV_DONTNEED;
zapping the pmd. Later, when the memory is hot, the implementation could
madvise(MADV_COLLAPSE) to re-back the memory by THPs to regain hugepage
coverage and dTLB performance. TCMalloc is such an implementation that
could benefit from this[2].
Only privately-mapped anon memory is supported for now, but additional
support for file, shmem, and HugeTLB high-granularity mappings[2] is
expected. File and tmpfs/shmem support would permit:
* Backing executable text by THPs. Current support provided by
CONFIG_READ_ONLY_THP_FOR_FS may take a long time on a large system which
might impair services from serving at their full rated load after
(re)starting. Tricks like mremap(2)'ing text onto anonymous memory to
immediately realize iTLB performance prevents page sharing and demand
paging, both of which increase steady state memory footprint. With
MADV_COLLAPSE, we get the best of both worlds: Peak upfront performance
and lower RAM footprints.
* Backing guest memory by hugapages after the memory contents have been
migrated in native-page-sized chunks to a new host, in a
userfaultfd-based live-migration stack.
[1] https://lore.kernel.org/linux-mm/d098c392-273a-36a4-1a29-59731cdf5d3d@google.com/
[2] https://github.com/google/tcmalloc/tree/master/tcmalloc
[jrdr.linux@gmail.com: avoid possible memory leak in failure path]
Link: https://lkml.kernel.org/r/20220713024109.62810-1-jrdr.linux@gmail.com
[zokeefe@google.com add missing kfree() to madvise_collapse()]
Link: https://lore.kernel.org/linux-mm/20220713024109.62810-1-jrdr.linux@gmail.com/
Link: https://lkml.kernel.org/r/20220713161851.1879439-1-zokeefe@google.com
[zokeefe@google.com: delay computation of hpage boundaries until use]]
Link: https://lkml.kernel.org/r/20220720140603.1958773-4-zokeefe@google.com
Link: https://lkml.kernel.org/r/20220706235936.2197195-10-zokeefe@google.com
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
Suggested-by: David Rientjes <rientjes@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
Pull tty/serial driver updates from Greg KH:
"Here are the big set of tty and serial driver changes for 5.18-rc1.
Nothing major, some more good cleanups from Jiri and 2 new serial
drivers. Highlights include:
- termbits cleanups
- export symbol cleanups and other core cleanups from Jiri Slaby
- new sunplus and mvebu uart drivers (amazing that people are still
creating new uarts...)
- samsung serial driver cleanups
- ldisc 29 is now "reserved" for experimental/development line
disciplines
- lots of other tiny fixes and cleanups to serial drivers and
bindings
All of these have been in linux-next for a while with no reported
issues"
* tag 'tty-5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (104 commits)
vt_ioctl: fix potential spectre v1 in VT_DISALLOCATE
serial: 8250: fix XOFF/XON sending when DMA is used
tty: serial: samsung: Add ARTPEC-8 support
dt-bindings: serial: samsung: Add ARTPEC-8 UART
serial: sc16is7xx: Clear RS485 bits in the shutdown
tty: serial: samsung: simplify getting OF match data
tty: serial: samsung: constify variables and pointers
tty: serial: samsung: constify s3c24xx_serial_drv_data members
tty: serial: samsung: constify UART name
tty: serial: samsung: constify s3c24xx_serial_drv_data
tty: serial: samsung: reduce number of casts
tty: serial: samsung: embed s3c2410_uartcfg in parent structure
tty: serial: samsung: embed s3c24xx_uart_info in parent structure
serial: 8250_tegra: mark acpi_device_id as unused with !ACPI
tty: serial: bcm63xx: use more precise Kconfig symbol
serial: SERIAL_SUNPLUS should depend on ARCH_SUNPLUS
tty: serial: jsm: fix two assignments in if conditions
tty: serial: jsm: remove redundant assignments to variable linestatus
serial: 8250_mtk: make two read-only arrays static const
serial: samsung_tty: do not unlock port->lock for uart_write_wakeup()
...
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MADV_DONTNEED historically rejects mlocked ranges, but with MLOCK_ONFAULT
and MCL_ONFAULT allowing to mlock without populating, there are valid use
cases for depopulating locked ranges as well.
Users mlock memory to protect secrets. There are allocators for secure
buffers that want in-use memory generally mlocked, but cleared and
invalidated memory to give up the physical pages. This could be done with
explicit munlock -> mlock calls on free -> alloc of course, but that adds
two unnecessary syscalls, heavy mmap_sem write locks, vma splits and
re-merges - only to get rid of the backing pages.
Users also mlockall(MCL_ONFAULT) to suppress sustained paging, but are
okay with on-demand initial population. It seems valid to selectively
free some memory during the lifetime of such a process, without having to
mess with its overall policy.
Why add a separate flag? Isn't this a pretty niche usecase?
- MADV_DONTNEED has been bailing on locked vmas forever. It's at least
conceivable that someone, somewhere is relying on mlock to protect
data from perhaps broader invalidation calls. Changing this behavior
now could lead to quiet data corruption.
- It also clarifies expectations around MADV_FREE and maybe
MADV_REMOVE. It avoids the situation where one quietly behaves
different than the others. MADV_FREE_LOCKED can be added later.
- The combination of mlock() and madvise() in the first place is
probably niche. But where it happens, I'd say that dropping pages
from a locked region once they don't contain secrets or won't page
anymore is much saner than relying on mlock to protect memory from
speculative or errant invalidation calls. It's just that we can't
change the default behavior because of the two previous points.
Given that, an explicit new flag seems to make the most sense.
[hannes@cmpxchg.org: fix mips build]
Link: https://lkml.kernel.org/r/20220304171912.305060-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove arch specific termbits.h as there are only trivial space
differences between include/uapi/asm-generic/termbits.h and
arch/xtensa/include/uapi/asm/termbits.h.
$ diff -u0 -b -B include/uapi/asm-generic/termbits.h arch/xtensa/include/uapi/asm/termbits.h
. --- include/uapi/asm-generic/termbits.h 2022-01-10 13:44:42.814107461 +0200
. +++ arch/xtensa/include/uapi/asm/termbits.h 2022-01-10 13:44:42.690106926 +0200
. @@ -2,2 +2,15 @@
. -#ifndef __ASM_GENERIC_TERMBITS_H
. -#define __ASM_GENERIC_TERMBITS_H
. +/*
. + * include/asm-xtensa/termbits.h
. + *
. + * Copied from SH.
. + *
. + * This file is subject to the terms and conditions of the GNU General Public
. + * License. See the file "COPYING" in the main directory of this archive
. + * for more details.
. + *
. + * Copyright (C) 2001 - 2005 Tensilica Inc.
. + */
. +
. +#ifndef _XTENSA_TERMBITS_H
. +#define _XTENSA_TERMBITS_H
. +
. @@ -200 +221 @@
. -#endif /* __ASM_GENERIC_TERMBITS_H */
. +#endif /* _XTENSA_TERMBITS_H */
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220222115604.7351-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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asm/shmbuf.h is currently excluded from the UAPI compile-test because of
the errors like follows:
HDRTEST usr/include/asm/shmbuf.h
In file included from ./usr/include/asm/shmbuf.h:6,
from <command-line>:
./usr/include/asm-generic/shmbuf.h:26:33: error: field ‘shm_perm’ has incomplete type
26 | struct ipc64_perm shm_perm; /* operation perms */
| ^~~~~~~~
./usr/include/asm-generic/shmbuf.h:27:9: error: unknown type name ‘size_t’
27 | size_t shm_segsz; /* size of segment (bytes) */
| ^~~~~~
./usr/include/asm-generic/shmbuf.h:40:9: error: unknown type name ‘__kernel_pid_t’
40 | __kernel_pid_t shm_cpid; /* pid of creator */
| ^~~~~~~~~~~~~~
./usr/include/asm-generic/shmbuf.h:41:9: error: unknown type name ‘__kernel_pid_t’
41 | __kernel_pid_t shm_lpid; /* pid of last operator */
| ^~~~~~~~~~~~~~
The errors can be fixed by replacing size_t with __kernel_size_t and by
including proper headers.
Then, remove the no-header-test entry from user/include/Makefile.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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linux/signal.h and asm/signal.h are currently excluded from the UAPI
compile-test because of the errors like follows:
HDRTEST usr/include/asm/signal.h
In file included from <command-line>:
./usr/include/asm/signal.h:103:9: error: unknown type name ‘size_t’
103 | size_t ss_size;
| ^~~~~~
The errors can be fixed by replacing size_t with __kernel_size_t.
Then, remove the no-header-test entries from user/include/Makefile.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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I. Background: Sparse Memory Mappings
When we manage sparse memory mappings dynamically in user space - also
sometimes involving MAP_NORESERVE - we want to dynamically populate/
discard memory inside such a sparse memory region. Example users are
hypervisors (especially implementing memory ballooning or similar
technologies like virtio-mem) and memory allocators. In addition, we want
to fail in a nice way (instead of generating SIGBUS) if populating does
not succeed because we are out of backend memory (which can happen easily
with file-based mappings, especially tmpfs and hugetlbfs).
While MADV_DONTNEED, MADV_REMOVE and FALLOC_FL_PUNCH_HOLE allow for
reliably discarding memory for most mapping types, there is no generic
approach to populate page tables and preallocate memory.
Although mmap() supports MAP_POPULATE, it is not applicable to the concept
of sparse memory mappings, where we want to populate/discard dynamically
and avoid expensive/problematic remappings. In addition, we never
actually report errors during the final populate phase - it is best-effort
only.
fallocate() can be used to preallocate file-based memory and fail in a
safe way. However, it cannot really be used for any private mappings on
anonymous files via memfd due to COW semantics. In addition, fallocate()
does not actually populate page tables, so we still always get pagefaults
on first access - which is sometimes undesired (i.e., real-time workloads)
and requires real prefaulting of page tables, not just a preallocation of
backend storage. There might be interesting use cases for sparse memory
regions along with mlockall(MCL_ONFAULT) which fallocate() cannot satisfy
as it does not prefault page tables.
II. On preallcoation/prefaulting from user space
Because we don't have a proper interface, what applications (like QEMU and
databases) end up doing is touching (i.e., reading+writing one byte to not
overwrite existing data) all individual pages.
However, that approach
1) Can result in wear on storage backing, because we end up reading/writing
each page; this is especially a problem for dax/pmem.
2) Can result in mmap_sem contention when prefaulting via multiple
threads.
3) Requires expensive signal handling, especially to catch SIGBUS in case
of hugetlbfs/shmem/file-backed memory. For example, this is
problematic in hypervisors like QEMU where SIGBUS handlers might already
be used by other subsystems concurrently to e.g, handle hardware errors.
"Simply" doing preallocation concurrently from other thread is not that
easy.
III. On MADV_WILLNEED
Extending MADV_WILLNEED is not an option because
1. It would change the semantics: "Expect access in the near future." and
"might be a good idea to read some pages" vs. "Definitely populate/
preallocate all memory and definitely fail on errors.".
2. Existing users (like virtio-balloon in QEMU when deflating the balloon)
don't want populate/prealloc semantics. They treat this rather as a hint
to give a little performance boost without too much overhead - and don't
expect that a lot of memory might get consumed or a lot of time
might be spent.
IV. MADV_POPULATE_READ and MADV_POPULATE_WRITE
Let's introduce MADV_POPULATE_READ and MADV_POPULATE_WRITE, inspired by
MAP_POPULATE, with the following semantics:
1. MADV_POPULATE_READ can be used to prefault page tables just like
manually reading each individual page. This will not break any COW
mappings. The shared zero page might get mapped and no backend storage
might get preallocated -- allocation might be deferred to
write-fault time. Especially shared file mappings require an explicit
fallocate() upfront to actually preallocate backend memory (blocks in
the file system) in case the file might have holes.
2. If MADV_POPULATE_READ succeeds, all page tables have been populated
(prefaulted) readable once.
3. MADV_POPULATE_WRITE can be used to preallocate backend memory and
prefault page tables just like manually writing (or
reading+writing) each individual page. This will break any COW
mappings -- e.g., the shared zeropage is never populated.
4. If MADV_POPULATE_WRITE succeeds, all page tables have been populated
(prefaulted) writable once.
5. MADV_POPULATE_READ and MADV_POPULATE_WRITE cannot be applied to special
mappings marked with VM_PFNMAP and VM_IO. Also, proper access
permissions (e.g., PROT_READ, PROT_WRITE) are required. If any such
mapping is encountered, madvise() fails with -EINVAL.
6. If MADV_POPULATE_READ or MADV_POPULATE_WRITE fails, some page tables
might have been populated.
7. MADV_POPULATE_READ and MADV_POPULATE_WRITE will return -EHWPOISON
when encountering a HW poisoned page in the range.
8. Similar to MAP_POPULATE, MADV_POPULATE_READ and MADV_POPULATE_WRITE
cannot protect from the OOM (Out Of Memory) handler killing the
process.
While the use case for MADV_POPULATE_WRITE is fairly obvious (i.e.,
preallocate memory and prefault page tables for VMs), one issue is that
whenever we prefault pages writable, the pages have to be marked dirty,
because the CPU could dirty them any time. while not a real problem for
hugetlbfs or dax/pmem, it can be a problem for shared file mappings: each
page will be marked dirty and has to be written back later when evicting.
MADV_POPULATE_READ allows for optimizing this scenario: Pre-read a whole
mapping from backend storage without marking it dirty, such that eviction
won't have to write it back. As discussed above, shared file mappings
might require an explciit fallocate() upfront to achieve
preallcoation+prepopulation.
Although sparse memory mappings are the primary use case, this will also
be useful for other preallocate/prefault use cases where MAP_POPULATE is
not desired or the semantics of MAP_POPULATE are not sufficient: as one
example, QEMU users can trigger preallocation/prefaulting of guest RAM
after the mapping was created -- and don't want errors to be silently
suppressed.
Looking at the history, MADV_POPULATE was already proposed in 2013 [1],
however, the main motivation back than was performance improvements --
which should also still be the case.
V. Single-threaded performance comparison
I did a short experiment, prefaulting page tables on completely *empty
mappings/files* and repeated the experiment 10 times. The results
correspond to the shortest execution time. In general, the performance
benefit for huge pages is negligible with small mappings.
V.1: Private mappings
POPULATE_READ and POPULATE_WRITE is fastest. Note that
Reading/POPULATE_READ will populate the shared zeropage where applicable
-- which result in short population times.
The fastest way to allocate backend storage (here: swap or huge pages) and
prefault page tables is POPULATE_WRITE.
V.2: Shared mappings
fallocate() is fastest, however, doesn't prefault page tables.
POPULATE_WRITE is faster than simple writes and read/writes.
POPULATE_READ is faster than simple reads.
Without a fd, the fastest way to allocate backend storage and prefault
page tables is POPULATE_WRITE. With an fd, the fastest way is usually
FALLOCATE+POPULATE_READ or FALLOCATE+POPULATE_WRITE respectively; one
exception are actual files: FALLOCATE+Read is slightly faster than
FALLOCATE+POPULATE_READ.
The fastest way to allocate backend storage prefault page tables is
FALLOCATE+POPULATE_WRITE -- except when dealing with actual files; then,
FALLOCATE+POPULATE_READ is fastest and won't directly mark all pages as
dirty.
v.3: Detailed results
==================================================
2 MiB MAP_PRIVATE:
**************************************************
Anon 4 KiB : Read : 0.119 ms
Anon 4 KiB : Write : 0.222 ms
Anon 4 KiB : Read/Write : 0.380 ms
Anon 4 KiB : POPULATE_READ : 0.060 ms
Anon 4 KiB : POPULATE_WRITE : 0.158 ms
Memfd 4 KiB : Read : 0.034 ms
Memfd 4 KiB : Write : 0.310 ms
Memfd 4 KiB : Read/Write : 0.362 ms
Memfd 4 KiB : POPULATE_READ : 0.039 ms
Memfd 4 KiB : POPULATE_WRITE : 0.229 ms
Memfd 2 MiB : Read : 0.030 ms
Memfd 2 MiB : Write : 0.030 ms
Memfd 2 MiB : Read/Write : 0.030 ms
Memfd 2 MiB : POPULATE_READ : 0.030 ms
Memfd 2 MiB : POPULATE_WRITE : 0.030 ms
tmpfs : Read : 0.033 ms
tmpfs : Write : 0.313 ms
tmpfs : Read/Write : 0.406 ms
tmpfs : POPULATE_READ : 0.039 ms
tmpfs : POPULATE_WRITE : 0.285 ms
file : Read : 0.033 ms
file : Write : 0.351 ms
file : Read/Write : 0.408 ms
file : POPULATE_READ : 0.039 ms
file : POPULATE_WRITE : 0.290 ms
hugetlbfs : Read : 0.030 ms
hugetlbfs : Write : 0.030 ms
hugetlbfs : Read/Write : 0.030 ms
hugetlbfs : POPULATE_READ : 0.030 ms
hugetlbfs : POPULATE_WRITE : 0.030 ms
**************************************************
4096 MiB MAP_PRIVATE:
**************************************************
Anon 4 KiB : Read : 237.940 ms
Anon 4 KiB : Write : 708.409 ms
Anon 4 KiB : Read/Write : 1054.041 ms
Anon 4 KiB : POPULATE_READ : 124.310 ms
Anon 4 KiB : POPULATE_WRITE : 572.582 ms
Memfd 4 KiB : Read : 136.928 ms
Memfd 4 KiB : Write : 963.898 ms
Memfd 4 KiB : Read/Write : 1106.561 ms
Memfd 4 KiB : POPULATE_READ : 78.450 ms
Memfd 4 KiB : POPULATE_WRITE : 805.881 ms
Memfd 2 MiB : Read : 357.116 ms
Memfd 2 MiB : Write : 357.210 ms
Memfd 2 MiB : Read/Write : 357.606 ms
Memfd 2 MiB : POPULATE_READ : 356.094 ms
Memfd 2 MiB : POPULATE_WRITE : 356.937 ms
tmpfs : Read : 137.536 ms
tmpfs : Write : 954.362 ms
tmpfs : Read/Write : 1105.954 ms
tmpfs : POPULATE_READ : 80.289 ms
tmpfs : POPULATE_WRITE : 822.826 ms
file : Read : 137.874 ms
file : Write : 987.025 ms
file : Read/Write : 1107.439 ms
file : POPULATE_READ : 80.413 ms
file : POPULATE_WRITE : 857.622 ms
hugetlbfs : Read : 355.607 ms
hugetlbfs : Write : 355.729 ms
hugetlbfs : Read/Write : 356.127 ms
hugetlbfs : POPULATE_READ : 354.585 ms
hugetlbfs : POPULATE_WRITE : 355.138 ms
**************************************************
2 MiB MAP_SHARED:
**************************************************
Anon 4 KiB : Read : 0.394 ms
Anon 4 KiB : Write : 0.348 ms
Anon 4 KiB : Read/Write : 0.400 ms
Anon 4 KiB : POPULATE_READ : 0.326 ms
Anon 4 KiB : POPULATE_WRITE : 0.273 ms
Anon 2 MiB : Read : 0.030 ms
Anon 2 MiB : Write : 0.030 ms
Anon 2 MiB : Read/Write : 0.030 ms
Anon 2 MiB : POPULATE_READ : 0.030 ms
Anon 2 MiB : POPULATE_WRITE : 0.030 ms
Memfd 4 KiB : Read : 0.412 ms
Memfd 4 KiB : Write : 0.372 ms
Memfd 4 KiB : Read/Write : 0.419 ms
Memfd 4 KiB : POPULATE_READ : 0.343 ms
Memfd 4 KiB : POPULATE_WRITE : 0.288 ms
Memfd 4 KiB : FALLOCATE : 0.137 ms
Memfd 4 KiB : FALLOCATE+Read : 0.446 ms
Memfd 4 KiB : FALLOCATE+Write : 0.330 ms
Memfd 4 KiB : FALLOCATE+Read/Write : 0.454 ms
Memfd 4 KiB : FALLOCATE+POPULATE_READ : 0.379 ms
Memfd 4 KiB : FALLOCATE+POPULATE_WRITE : 0.268 ms
Memfd 2 MiB : Read : 0.030 ms
Memfd 2 MiB : Write : 0.030 ms
Memfd 2 MiB : Read/Write : 0.030 ms
Memfd 2 MiB : POPULATE_READ : 0.030 ms
Memfd 2 MiB : POPULATE_WRITE : 0.030 ms
Memfd 2 MiB : FALLOCATE : 0.030 ms
Memfd 2 MiB : FALLOCATE+Read : 0.031 ms
Memfd 2 MiB : FALLOCATE+Write : 0.031 ms
Memfd 2 MiB : FALLOCATE+Read/Write : 0.031 ms
Memfd 2 MiB : FALLOCATE+POPULATE_READ : 0.030 ms
Memfd 2 MiB : FALLOCATE+POPULATE_WRITE : 0.030 ms
tmpfs : Read : 0.416 ms
tmpfs : Write : 0.369 ms
tmpfs : Read/Write : 0.425 ms
tmpfs : POPULATE_READ : 0.346 ms
tmpfs : POPULATE_WRITE : 0.295 ms
tmpfs : FALLOCATE : 0.139 ms
tmpfs : FALLOCATE+Read : 0.447 ms
tmpfs : FALLOCATE+Write : 0.333 ms
tmpfs : FALLOCATE+Read/Write : 0.454 ms
tmpfs : FALLOCATE+POPULATE_READ : 0.380 ms
tmpfs : FALLOCATE+POPULATE_WRITE : 0.272 ms
file : Read : 0.191 ms
file : Write : 0.511 ms
file : Read/Write : 0.524 ms
file : POPULATE_READ : 0.196 ms
file : POPULATE_WRITE : 0.434 ms
file : FALLOCATE : 0.004 ms
file : FALLOCATE+Read : 0.197 ms
file : FALLOCATE+Write : 0.554 ms
file : FALLOCATE+Read/Write : 0.480 ms
file : FALLOCATE+POPULATE_READ : 0.201 ms
file : FALLOCATE+POPULATE_WRITE : 0.381 ms
hugetlbfs : Read : 0.030 ms
hugetlbfs : Write : 0.030 ms
hugetlbfs : Read/Write : 0.030 ms
hugetlbfs : POPULATE_READ : 0.030 ms
hugetlbfs : POPULATE_WRITE : 0.030 ms
hugetlbfs : FALLOCATE : 0.030 ms
hugetlbfs : FALLOCATE+Read : 0.031 ms
hugetlbfs : FALLOCATE+Write : 0.031 ms
hugetlbfs : FALLOCATE+Read/Write : 0.030 ms
hugetlbfs : FALLOCATE+POPULATE_READ : 0.030 ms
hugetlbfs : FALLOCATE+POPULATE_WRITE : 0.030 ms
**************************************************
4096 MiB MAP_SHARED:
**************************************************
Anon 4 KiB : Read : 1053.090 ms
Anon 4 KiB : Write : 913.642 ms
Anon 4 KiB : Read/Write : 1060.350 ms
Anon 4 KiB : POPULATE_READ : 893.691 ms
Anon 4 KiB : POPULATE_WRITE : 782.885 ms
Anon 2 MiB : Read : 358.553 ms
Anon 2 MiB : Write : 358.419 ms
Anon 2 MiB : Read/Write : 357.992 ms
Anon 2 MiB : POPULATE_READ : 357.533 ms
Anon 2 MiB : POPULATE_WRITE : 357.808 ms
Memfd 4 KiB : Read : 1078.144 ms
Memfd 4 KiB : Write : 942.036 ms
Memfd 4 KiB : Read/Write : 1100.391 ms
Memfd 4 KiB : POPULATE_READ : 925.829 ms
Memfd 4 KiB : POPULATE_WRITE : 804.394 ms
Memfd 4 KiB : FALLOCATE : 304.632 ms
Memfd 4 KiB : FALLOCATE+Read : 1163.359 ms
Memfd 4 KiB : FALLOCATE+Write : 933.186 ms
Memfd 4 KiB : FALLOCATE+Read/Write : 1187.304 ms
Memfd 4 KiB : FALLOCATE+POPULATE_READ : 1013.660 ms
Memfd 4 KiB : FALLOCATE+POPULATE_WRITE : 794.560 ms
Memfd 2 MiB : Read : 358.131 ms
Memfd 2 MiB : Write : 358.099 ms
Memfd 2 MiB : Read/Write : 358.250 ms
Memfd 2 MiB : POPULATE_READ : 357.563 ms
Memfd 2 MiB : POPULATE_WRITE : 357.334 ms
Memfd 2 MiB : FALLOCATE : 356.735 ms
Memfd 2 MiB : FALLOCATE+Read : 358.152 ms
Memfd 2 MiB : FALLOCATE+Write : 358.331 ms
Memfd 2 MiB : FALLOCATE+Read/Write : 358.018 ms
Memfd 2 MiB : FALLOCATE+POPULATE_READ : 357.286 ms
Memfd 2 MiB : FALLOCATE+POPULATE_WRITE : 357.523 ms
tmpfs : Read : 1087.265 ms
tmpfs : Write : 950.840 ms
tmpfs : Read/Write : 1107.567 ms
tmpfs : POPULATE_READ : 922.605 ms
tmpfs : POPULATE_WRITE : 810.094 ms
tmpfs : FALLOCATE : 306.320 ms
tmpfs : FALLOCATE+Read : 1169.796 ms
tmpfs : FALLOCATE+Write : 933.730 ms
tmpfs : FALLOCATE+Read/Write : 1191.610 ms
tmpfs : FALLOCATE+POPULATE_READ : 1020.474 ms
tmpfs : FALLOCATE+POPULATE_WRITE : 798.945 ms
file : Read : 654.101 ms
file : Write : 1259.142 ms
file : Read/Write : 1289.509 ms
file : POPULATE_READ : 661.642 ms
file : POPULATE_WRITE : 1106.816 ms
file : FALLOCATE : 1.864 ms
file : FALLOCATE+Read : 656.328 ms
file : FALLOCATE+Write : 1153.300 ms
file : FALLOCATE+Read/Write : 1180.613 ms
file : FALLOCATE+POPULATE_READ : 668.347 ms
file : FALLOCATE+POPULATE_WRITE : 996.143 ms
hugetlbfs : Read : 357.245 ms
hugetlbfs : Write : 357.413 ms
hugetlbfs : Read/Write : 357.120 ms
hugetlbfs : POPULATE_READ : 356.321 ms
hugetlbfs : POPULATE_WRITE : 356.693 ms
hugetlbfs : FALLOCATE : 355.927 ms
hugetlbfs : FALLOCATE+Read : 357.074 ms
hugetlbfs : FALLOCATE+Write : 357.120 ms
hugetlbfs : FALLOCATE+Read/Write : 356.983 ms
hugetlbfs : FALLOCATE+POPULATE_READ : 356.413 ms
hugetlbfs : FALLOCATE+POPULATE_WRITE : 356.266 ms
**************************************************
[1] https://lkml.org/lkml/2013/6/27/698
[akpm@linux-foundation.org: coding style fixes]
Link: https://lkml.kernel.org/r/20210419135443.12822-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rolf Eike Beer <eike-kernel@sf-tec.de>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Most architectures with the exception of alpha, mips, parisc and
sparc use the same values for these flags. Move their definitions into
asm-generic/signal-defs.h and allow the architectures with non-standard
values to override them. Also, document the non-standard flag values
in order to make it easier to add new generic flags in the future.
A consequence of this change is that on powerpc and x86, the constants'
values aside from SA_RESETHAND change signedness from unsigned
to signed. This is not expected to impact realistic use of these
constants. In particular the typical use of the constants where they
are or'ed together and assigned to sa_flags (or another int variable)
would not be affected.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Link: https://linux-review.googlesource.com/id/Ia3849f18b8009bf41faca374e701cdca36974528
Link: https://lkml.kernel.org/r/b6d0d1ec34f9ee93e1105f14f288fba5f89d1f24.1605235762.git.pcc@google.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
|
|
Use one of the reserved slots in struct user_pt_regs to return syscall
number in the GPR regset. Update syscall number from the GPR regset only
when it's non-zero.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
|
|
There's no implementation for set_except_vector function in the xtensa
code. Drop its declaration.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
|
|
Userspace cannot compile <asm/sembuf.h> due to some missing type
definitions. For example, building it for x86 fails as follows:
CC usr/include/asm/sembuf.h.s
In file included from <command-line>:32:0:
usr/include/asm/sembuf.h:17:20: error: field `sem_perm' has incomplete type
struct ipc64_perm sem_perm; /* permissions .. see ipc.h */
^~~~~~~~
usr/include/asm/sembuf.h:24:2: error: unknown type name `__kernel_time_t'
__kernel_time_t sem_otime; /* last semop time */
^~~~~~~~~~~~~~~
usr/include/asm/sembuf.h:25:2: error: unknown type name `__kernel_ulong_t'
__kernel_ulong_t __unused1;
^~~~~~~~~~~~~~~~
usr/include/asm/sembuf.h:26:2: error: unknown type name `__kernel_time_t'
__kernel_time_t sem_ctime; /* last change time */
^~~~~~~~~~~~~~~
usr/include/asm/sembuf.h:27:2: error: unknown type name `__kernel_ulong_t'
__kernel_ulong_t __unused2;
^~~~~~~~~~~~~~~~
usr/include/asm/sembuf.h:29:2: error: unknown type name `__kernel_ulong_t'
__kernel_ulong_t sem_nsems; /* no. of semaphores in array */
^~~~~~~~~~~~~~~~
usr/include/asm/sembuf.h:30:2: error: unknown type name `__kernel_ulong_t'
__kernel_ulong_t __unused3;
^~~~~~~~~~~~~~~~
usr/include/asm/sembuf.h:31:2: error: unknown type name `__kernel_ulong_t'
__kernel_ulong_t __unused4;
^~~~~~~~~~~~~~~~
It is just a matter of missing include directive.
Include <asm/ipcbuf.h> to make it self-contained, and add it to
the compile-test coverage.
Link: http://lkml.kernel.org/r/20191030063855.9989-3-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Userspace cannot compile <asm/msgbuf.h> due to some missing type
definitions. For example, building it for x86 fails as follows:
CC usr/include/asm/msgbuf.h.s
In file included from usr/include/asm/msgbuf.h:6:0,
from <command-line>:32:
usr/include/asm-generic/msgbuf.h:25:20: error: field `msg_perm' has incomplete type
struct ipc64_perm msg_perm;
^~~~~~~~
usr/include/asm-generic/msgbuf.h:27:2: error: unknown type name `__kernel_time_t'
__kernel_time_t msg_stime; /* last msgsnd time */
^~~~~~~~~~~~~~~
usr/include/asm-generic/msgbuf.h:28:2: error: unknown type name `__kernel_time_t'
__kernel_time_t msg_rtime; /* last msgrcv time */
^~~~~~~~~~~~~~~
usr/include/asm-generic/msgbuf.h:29:2: error: unknown type name `__kernel_time_t'
__kernel_time_t msg_ctime; /* last change time */
^~~~~~~~~~~~~~~
usr/include/asm-generic/msgbuf.h:41:2: error: unknown type name `__kernel_pid_t'
__kernel_pid_t msg_lspid; /* pid of last msgsnd */
^~~~~~~~~~~~~~
usr/include/asm-generic/msgbuf.h:42:2: error: unknown type name `__kernel_pid_t'
__kernel_pid_t msg_lrpid; /* last receive pid */
^~~~~~~~~~~~~~
It is just a matter of missing include directive.
Include <asm/ipcbuf.h> to make it self-contained, and add it to
the compile-test coverage.
Link: http://lkml.kernel.org/r/20191030063855.9989-2-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Userspace cannot compile <asm/ipcbuf.h> due to some missing type
definitions. For example, building it for x86 fails as follows:
CC usr/include/asm/ipcbuf.h.s
In file included from usr/include/asm/ipcbuf.h:1:0,
from <command-line>:32:
usr/include/asm-generic/ipcbuf.h:21:2: error: unknown type name `__kernel_key_t'
__kernel_key_t key;
^~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:22:2: error: unknown type name `__kernel_uid32_t'
__kernel_uid32_t uid;
^~~~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:23:2: error: unknown type name `__kernel_gid32_t'
__kernel_gid32_t gid;
^~~~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:24:2: error: unknown type name `__kernel_uid32_t'
__kernel_uid32_t cuid;
^~~~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:25:2: error: unknown type name `__kernel_gid32_t'
__kernel_gid32_t cgid;
^~~~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:26:2: error: unknown type name `__kernel_mode_t'
__kernel_mode_t mode;
^~~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:28:35: error: `__kernel_mode_t' undeclared here (not in a function)
unsigned char __pad1[4 - sizeof(__kernel_mode_t)];
^~~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:31:2: error: unknown type name `__kernel_ulong_t'
__kernel_ulong_t __unused1;
^~~~~~~~~~~~~~~~
usr/include/asm-generic/ipcbuf.h:32:2: error: unknown type name `__kernel_ulong_t'
__kernel_ulong_t __unused2;
^~~~~~~~~~~~~~~~
It is just a matter of missing include directive.
Include <linux/posix_types.h> to make it self-contained, and add it to
the compile-test coverage.
Link: http://lkml.kernel.org/r/20191030063855.9989-1-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
When a process expects no accesses to a certain memory range for a long
time, it could hint kernel that the pages can be reclaimed instantly but
data should be preserved for future use. This could reduce workingset
eviction so it ends up increasing performance.
This patch introduces the new MADV_PAGEOUT hint to madvise(2) syscall.
MADV_PAGEOUT can be used by a process to mark a memory range as not
expected to be used for a long time so that kernel reclaims *any LRU*
pages instantly. The hint can help kernel in deciding which pages to
evict proactively.
A note: It doesn't apply SWAP_CLUSTER_MAX LRU page isolation limit
intentionally because it's automatically bounded by PMD size. If PMD
size(e.g., 256) makes some trouble, we could fix it later by limit it to
SWAP_CLUSTER_MAX[1].
- man-page material
MADV_PAGEOUT (since Linux x.x)
Do not expect access in the near future so pages in the specified
regions could be reclaimed instantly regardless of memory pressure.
Thus, access in the range after successful operation could cause
major page fault but never lose the up-to-date contents unlike
MADV_DONTNEED. Pages belonging to a shared mapping are only processed
if a write access is allowed for the calling process.
MADV_PAGEOUT cannot be applied to locked pages, Huge TLB pages, or
VM_PFNMAP pages.
[1] https://lore.kernel.org/lkml/20190710194719.GS29695@dhcp22.suse.cz/
[minchan@kernel.org: clear PG_active on MADV_PAGEOUT]
Link: http://lkml.kernel.org/r/20190802200643.GA181880@google.com
[akpm@linux-foundation.org: resolve conflicts with hmm.git]
Link: http://lkml.kernel.org/r/20190726023435.214162-5-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Daniel Colascione <dancol@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Oleksandr Natalenko <oleksandr@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Sonny Rao <sonnyrao@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tim Murray <timmurray@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Patch series "Introduce MADV_COLD and MADV_PAGEOUT", v7.
- Background
The Android terminology used for forking a new process and starting an app
from scratch is a cold start, while resuming an existing app is a hot
start. While we continually try to improve the performance of cold
starts, hot starts will always be significantly less power hungry as well
as faster so we are trying to make hot start more likely than cold start.
To increase hot start, Android userspace manages the order that apps
should be killed in a process called ActivityManagerService.
ActivityManagerService tracks every Android app or service that the user
could be interacting with at any time and translates that into a ranked
list for lmkd(low memory killer daemon). They are likely to be killed by
lmkd if the system has to reclaim memory. In that sense they are similar
to entries in any other cache. Those apps are kept alive for
opportunistic performance improvements but those performance improvements
will vary based on the memory requirements of individual workloads.
- Problem
Naturally, cached apps were dominant consumers of memory on the system.
However, they were not significant consumers of swap even though they are
good candidate for swap. Under investigation, swapping out only begins
once the low zone watermark is hit and kswapd wakes up, but the overall
allocation rate in the system might trip lmkd thresholds and cause a
cached process to be killed(we measured performance swapping out vs.
zapping the memory by killing a process. Unsurprisingly, zapping is 10x
times faster even though we use zram which is much faster than real
storage) so kill from lmkd will often satisfy the high zone watermark,
resulting in very few pages actually being moved to swap.
- Approach
The approach we chose was to use a new interface to allow userspace to
proactively reclaim entire processes by leveraging platform information.
This allowed us to bypass the inaccuracy of the kernel’s LRUs for pages
that are known to be cold from userspace and to avoid races with lmkd by
reclaiming apps as soon as they entered the cached state. Additionally,
it could provide many chances for platform to use much information to
optimize memory efficiency.
To achieve the goal, the patchset introduce two new options for madvise.
One is MADV_COLD which will deactivate activated pages and the other is
MADV_PAGEOUT which will reclaim private pages instantly. These new
options complement MADV_DONTNEED and MADV_FREE by adding non-destructive
ways to gain some free memory space. MADV_PAGEOUT is similar to
MADV_DONTNEED in a way that it hints the kernel that memory region is not
currently needed and should be reclaimed immediately; MADV_COLD is similar
to MADV_FREE in a way that it hints the kernel that memory region is not
currently needed and should be reclaimed when memory pressure rises.
This patch (of 5):
When a process expe |
