diff options
| -rw-r--r-- | Documentation/blockdev/zram.txt | 6 | ||||
| -rw-r--r-- | drivers/block/zram/zram_drv.c | 87 | ||||
| -rw-r--r-- | drivers/block/zram/zram_drv.h | 9 |
3 files changed, 69 insertions, 33 deletions
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 1c0c08d9206b..4fced8a21307 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -201,8 +201,8 @@ File /sys/block/zram<id>/mm_stat The stat file represents device's mm statistics. It consists of a single line of text and contains the following stats separated by whitespace: orig_data_size uncompressed size of data stored in this disk. - This excludes zero-filled pages (zero_pages) since no - memory is allocated for them. + This excludes same-element-filled pages (same_pages) since + no memory is allocated for them. Unit: bytes compr_data_size compressed size of data stored in this disk mem_used_total the amount of memory allocated for this disk. This @@ -214,7 +214,7 @@ line of text and contains the following stats separated by whitespace: the compressed data mem_used_max the maximum amount of memory zram have consumed to store the data - zero_pages the number of zero filled pages written to this disk. + same_pages the number of same element filled pages written to this disk. No memory is allocated for such pages. pages_compacted the number of pages freed during compaction 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 */ |