From a09759acaacf6cf738e1bc6c66d41485c87fd371 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Fri, 24 Feb 2017 14:56:47 -0800 Subject: zram: remove waitqueue for IO done zram_reset_device() waits for ongoing writepage pages to be completed by zram->refcount logic. However, it's pointless because before the reset, we prevent further opening of zram by zram->claim and flush all of pending IO by fsync_bdev so there should be no pending IO at the zram_reset_device(). So let's remove that code which is even broken due to the lack of wake_up elsewhere. Link: http://lkml.kernel.org/r/1485145031-11661-1-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim Reviewed-by: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/block/zram/zram_drv.c | 40 +++------------------------------------- drivers/block/zram/zram_drv.h | 3 --- 2 files changed, 3 insertions(+), 40 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index c73fede582f7..662d62878e47 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -391,18 +391,6 @@ static DEVICE_ATTR_RO(io_stat); static DEVICE_ATTR_RO(mm_stat); static DEVICE_ATTR_RO(debug_stat); -static inline bool zram_meta_get(struct zram *zram) -{ - if (atomic_inc_not_zero(&zram->refcount)) - return true; - return false; -} - -static inline void zram_meta_put(struct zram *zram) -{ - atomic_dec(&zram->refcount); -} - static void zram_meta_free(struct zram_meta *meta, u64 disksize) { size_t num_pages = disksize >> PAGE_SHIFT; @@ -859,22 +847,17 @@ static blk_qc_t zram_make_request(struct request_queue *queue, struct bio *bio) { struct zram *zram = queue->queuedata; - if (unlikely(!zram_meta_get(zram))) - goto error; - blk_queue_split(queue, &bio, queue->bio_split); if (!valid_io_request(zram, bio->bi_iter.bi_sector, bio->bi_iter.bi_size)) { atomic64_inc(&zram->stats.invalid_io); - goto put_zram; + goto error; } __zram_make_request(zram, bio); - zram_meta_put(zram); return BLK_QC_T_NONE; -put_zram: - zram_meta_put(zram); + error: bio_io_error(bio); return BLK_QC_T_NONE; @@ -904,13 +887,11 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, struct bio_vec bv; zram = bdev->bd_disk->private_data; - if (unlikely(!zram_meta_get(zram))) - goto out; if (!valid_io_request(zram, sector, PAGE_SIZE)) { atomic64_inc(&zram->stats.invalid_io); err = -EINVAL; - goto put_zram; + goto out; } index = sector >> SECTORS_PER_PAGE_SHIFT; @@ -921,8 +902,6 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, bv.bv_offset = 0; err = zram_bvec_rw(zram, &bv, index, offset, is_write); -put_zram: - zram_meta_put(zram); out: /* * If I/O fails, just return error(ie, non-zero) without @@ -955,17 +934,6 @@ static void zram_reset_device(struct zram *zram) meta = zram->meta; comp = zram->comp; disksize = zram->disksize; - /* - * Refcount will go down to 0 eventually and r/w handler - * cannot handle further I/O so it will bail out by - * check zram_meta_get. - */ - zram_meta_put(zram); - /* - * We want to free zram_meta in process context to avoid - * deadlock between reclaim path and any other locks. - */ - wait_event(zram->io_done, atomic_read(&zram->refcount) == 0); /* Reset stats */ memset(&zram->stats, 0, sizeof(zram->stats)); @@ -1013,8 +981,6 @@ static ssize_t disksize_store(struct device *dev, goto out_destroy_comp; } - init_waitqueue_head(&zram->io_done); - atomic_set(&zram->refcount, 1); zram->meta = meta; zram->comp = comp; zram->disksize = disksize; diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index 74fcf10da374..2692554b7737 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -106,9 +106,6 @@ struct zram { unsigned long limit_pages; struct zram_stats stats; - atomic_t refcount; /* refcount for zram_meta */ - /* wait all IO under all of cpu are done */ - wait_queue_head_t io_done; /* * This is the limit on amount of *uncompressed* worth of data * we can store in a disk. -- cgit v1.2.3 From 8e19d540d107ee897eb9a874844060c94e2376c0 Mon Sep 17 00:00:00 2001 From: zhouxianrong Date: Fri, 24 Feb 2017 14:59:27 -0800 Subject: zram: extend zero pages to same element pages The idea is that without doing more calculations we extend zero pages to same element pages for zram. zero page is special case of same element page with zero element. 1. the test is done under android 7.0 2. startup too many applications circularly 3. sample the zero pages, same pages (none-zero element) and total pages in function page_zero_filled the result is listed as below: ZERO SAME TOTAL 36214 17842 598196 ZERO/TOTAL SAME/TOTAL (ZERO+SAME)/TOTAL ZERO/SAME AVERAGE 0.060631909 0.024990816 0.085622726 2.663825038 STDEV 0.00674612 0.005887625 0.009707034 2.115881328 MAX 0.069698422 0.030046087 0.094975336 7.56043956 MIN 0.03959586 0.007332205 0.056055193 1.928985507 from the above data, the benefit is about 2.5% and up to 3% of total swapout pages. The defect of the patch is that when we recovery a page from non-zero element the operations are low efficient for partial read. This patch extends zero_page to same_page so if there is any user to have monitored zero_pages, he will be surprised if the number is increased but it's not harmful, I believe. [minchan@kernel.org: do not free same element pages in zram_meta_free] Link: http://lkml.kernel.org/r/20170207065741.GA2567@bbox Link: http://lkml.kernel.org/r/1483692145-75357-1-git-send-email-zhouxianrong@huawei.com Link: http://lkml.kernel.org/r/1486307804-27903-1-git-send-email-minchan@kernel.org Signed-off-by: zhouxianrong Signed-off-by: Minchan Kim Cc: Sergey Senozhatsky Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/block/zram/zram_drv.c | 87 +++++++++++++++++++++++++++++-------------- drivers/block/zram/zram_drv.h | 9 +++-- 2 files changed, 66 insertions(+), 30 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 662d62878e47..e27d89a36c34 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -74,6 +74,17 @@ static void zram_clear_flag(struct zram_meta *meta, u32 index, meta->table[index].value &= ~BIT(flag); } +static inline void zram_set_element(struct zram_meta *meta, u32 index, + unsigned long element) +{ + meta->table[index].element = element; +} + +static inline void zram_clear_element(struct zram_meta *meta, u32 index) +{ + meta->table[index].element = 0; +} + static size_t zram_get_obj_size(struct zram_meta *meta, u32 index) { return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1); @@ -146,31 +157,46 @@ static inline void update_used_max(struct zram *zram, } while (old_max != cur_max); } -static bool page_zero_filled(void *ptr) +static inline void zram_fill_page(char *ptr, unsigned long len, + unsigned long value) +{ + int i; + unsigned long *page = (unsigned long *)ptr; + + WARN_ON_ONCE(!IS_ALIGNED(len, sizeof(unsigned long))); + + if (likely(value == 0)) { + memset(ptr, 0, len); + } else { + for (i = 0; i < len / sizeof(*page); i++) + page[i] = value; + } +} + +static bool page_same_filled(void *ptr, unsigned long *element) { unsigned int pos; unsigned long *page; page = (unsigned long *)ptr; - for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) { - if (page[pos]) + for (pos = 0; pos < PAGE_SIZE / sizeof(*page) - 1; pos++) { + if (page[pos] != page[pos + 1]) return false; } + *element = page[pos]; + return true; } -static void handle_zero_page(struct bio_vec *bvec) +static void handle_same_page(struct bio_vec *bvec, unsigned long element) { struct page *page = bvec->bv_page; void *user_mem; user_mem = kmap_atomic(page); - if (is_partial_io(bvec)) - memset(user_mem + bvec->bv_offset, 0, bvec->bv_len); - else - clear_page(user_mem); + zram_fill_page(user_mem + bvec->bv_offset, bvec->bv_len, element); kunmap_atomic(user_mem); flush_dcache_page(page); @@ -363,7 +389,7 @@ static ssize_t mm_stat_show(struct device *dev, mem_used << PAGE_SHIFT, zram->limit_pages << PAGE_SHIFT, max_used << PAGE_SHIFT, - (u64)atomic64_read(&zram->stats.zero_pages), + (u64)atomic64_read(&zram->stats.same_pages), pool_stats.pages_compacted); up_read(&zram->init_lock); @@ -399,8 +425,11 @@ static void zram_meta_free(struct zram_meta *meta, u64 disksize) /* Free all pages that are still in this zram device */ for (index = 0; index < num_pages; index++) { unsigned long handle = meta->table[index].handle; - - if (!handle) + /* + * No memory is allocated for same element filled pages. + * Simply clear same page flag. + */ + if (!handle || zram_test_flag(meta, index, ZRAM_SAME)) continue; zs_free(meta->mem_pool, handle); @@ -450,18 +479,20 @@ static void zram_free_page(struct zram *zram, size_t index) struct zram_meta *meta = zram->meta; unsigned long handle = meta->table[index].handle; - if (unlikely(!handle)) { - /* - * No memory is allocated for zero filled pages. - * Simply clear zero page flag. - */ - if (zram_test_flag(meta, index, ZRAM_ZERO)) { - zram_clear_flag(meta, index, ZRAM_ZERO); - atomic64_dec(&zram->stats.zero_pages); - } + /* + * No memory is allocated for same element filled pages. + * Simply clear same page flag. + */ + if (zram_test_flag(meta, index, ZRAM_SAME)) { + zram_clear_flag(meta, index, ZRAM_SAME); + zram_clear_element(meta, index); + atomic64_dec(&zram->stats.same_pages); return; } + if (!handle) + return; + zs_free(meta->mem_pool, handle); atomic64_sub(zram_get_obj_size(meta, index), @@ -484,9 +515,9 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index) handle = meta->table[index].handle; size = zram_get_obj_size(meta, index); - if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) { + if (!handle || zram_test_flag(meta, index, ZRAM_SAME)) { bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value); - clear_page(mem); + zram_fill_page(mem, PAGE_SIZE, meta->table[index].element); return 0; } @@ -522,9 +553,9 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value); if (unlikely(!meta->table[index].handle) || - zram_test_flag(meta, index, ZRAM_ZERO)) { + zram_test_flag(meta, index, ZRAM_SAME)) { bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value); - handle_zero_page(bvec); + handle_same_page(bvec, meta->table[index].element); return 0; } bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value); @@ -572,6 +603,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, struct zram_meta *meta = zram->meta; struct zcomp_strm *zstrm = NULL; unsigned long alloced_pages; + unsigned long element; page = bvec->bv_page; if (is_partial_io(bvec)) { @@ -600,16 +632,17 @@ compress_again: uncmem = user_mem; } - if (page_zero_filled(uncmem)) { + if (page_same_filled(uncmem, &element)) { if (user_mem) kunmap_atomic(user_mem); /* Free memory associated with this sector now. */ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value); zram_free_page(zram, index); - zram_set_flag(meta, index, ZRAM_ZERO); + zram_set_flag(meta, index, ZRAM_SAME); + zram_set_element(meta, index, element); bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value); - atomic64_inc(&zram->stats.zero_pages); + atomic64_inc(&zram->stats.same_pages); ret = 0; goto out; } diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index 2692554b7737..caeff51f1571 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -61,7 +61,7 @@ static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; /* Flags for zram pages (table[page_no].value) */ enum zram_pageflags { /* Page consists entirely of zeros */ - ZRAM_ZERO = ZRAM_FLAG_SHIFT, + ZRAM_SAME = ZRAM_FLAG_SHIFT, ZRAM_ACCESS, /* page is now accessed */ __NR_ZRAM_PAGEFLAGS, @@ -71,7 +71,10 @@ enum zram_pageflags { /* Allocated for each disk page */ struct zram_table_entry { - unsigned long handle; + union { + unsigned long handle; + unsigned long element; + }; unsigned long value; }; @@ -83,7 +86,7 @@ struct zram_stats { atomic64_t failed_writes; /* can happen when memory is too low */ atomic64_t invalid_io; /* non-page-aligned I/O requests */ atomic64_t notify_free; /* no. of swap slot free notifications */ - atomic64_t zero_pages; /* no. of zero filled pages */ + atomic64_t same_pages; /* no. of same element filled pages */ atomic64_t pages_stored; /* no. of pages currently stored */ atomic_long_t max_used_pages; /* no. of maximum pages stored */ atomic64_t writestall; /* no. of write slow paths */ -- cgit v1.2.3