Re: [PATCH zram] extend zero pages to same element pages

From: Minchan Kim
Date: Thu Jan 05 2017 - 00:39:15 EST

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In reply to: zhouxianrong: "[PATCH zram] extend zero pages to same element pages"
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Hello,

To me, it's a good idea although I didn't look at code in detail. :)

Could you resend it as formal patch?
Please include description, number that how we can save memory in your
workload and you name for Signed-off-by.
As well, please Cc sergey.senozhatsky@xxxxxxxxx and akpm@xxxxxxxxxxxxxxxxxxxx
next time.

Thanks!

On Wed, Jan 04, 2017 at 02:20:05PM +0800, zhouxianrong@xxxxxxxxxx wrote:
> From: z00281421 <z00281421@xxxxxxxxxxxxxxxxxxxx>
>
>
> Signed-off-by: z00281421 <z00281421@xxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/block/zram/zram_drv.c | 67 ++++++++++++++++++++++++++---------------
> drivers/block/zram/zram_drv.h | 11 ++++---
> 2 files changed, 49 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 15f58ab..c3af69a 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -94,6 +94,17 @@ 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);
> @@ -158,31 +169,31 @@ static inline void update_used_max(struct zram *zram,
> } while (old_max != cur_max);
> }
>
> -static bool page_zero_filled(void *ptr)
> +static bool page_same_filled(void *ptr)
> {
> unsigned int pos;
> unsigned long *page;
>
> page = (unsigned long *)ptr;
>
> - for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
> - if (page[pos])
> + for (pos = PAGE_SIZE / sizeof(unsigned long) - 1; pos > 0; pos--) {
> + if (page[pos] != page[pos - 1])
> return false;
> }
>
> 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);
> + memset(user_mem + bvec->bv_offset, (char)element, bvec->bv_len);
> else
> - clear_page(user_mem);
> + memset(user_mem, (char)element, PAGE_SIZE);
> kunmap_atomic(user_mem);
>
> flush_dcache_page(page);
> @@ -431,7 +442,7 @@ 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);
>
> @@ -464,7 +475,7 @@ static ssize_t debug_stat_show(struct device *dev,
> ZRAM_ATTR_RO(failed_writes);
> ZRAM_ATTR_RO(invalid_io);
> ZRAM_ATTR_RO(notify_free);
> -ZRAM_ATTR_RO(zero_pages);
> +ZRAM_ATTR_RO(same_pages);
> ZRAM_ATTR_RO(compr_data_size);
>
> static inline bool zram_meta_get(struct zram *zram)
> @@ -538,18 +549,20 @@ 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),
> @@ -572,9 +585,9 @@ 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);
> + memset(mem, (char)meta->table[index].element, PAGE_SIZE);
> return 0;
> }
>
> @@ -610,9 +623,9 @@ 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);
> @@ -688,16 +701,20 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> uncmem = user_mem;
> }
>
> - if (page_zero_filled(uncmem)) {
> + if (page_same_filled(uncmem)) {
> + unsigned long element;
> +
> + element = uncmem[0];
> 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;
> }
> @@ -1203,7 +1220,7 @@ static int zram_open(struct block_device *bdev, fmode_t mode)
> &dev_attr_compact.attr,
> &dev_attr_invalid_io.attr,
> &dev_attr_notify_free.attr,
> - &dev_attr_zero_pages.attr,
> + &dev_attr_same_pages.attr,
> &dev_attr_orig_data_size.attr,
> &dev_attr_compr_data_size.attr,
> &dev_attr_mem_used_total.attr,
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index 74fcf10..4bb92e1 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -60,8 +60,8 @@
>
> /* Flags for zram pages (table[page_no].value) */
> enum zram_pageflags {
> - /* Page consists entirely of zeros */
> - ZRAM_ZERO = ZRAM_FLAG_SHIFT,
> + /* Page consists entirely of same elements */
> + 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 */
> --
> 1.7.9.5
>

Next message: Minchan Kim: "Re: [PATCH 2/7] mm, vmscan: add active list aging tracepoint"
Previous message: Xu, Even: "RE: [PATCH 7/7] misc: intel-ish-client: add intel ishtp clients driver"
In reply to: zhouxianrong: "[PATCH zram] extend zero pages to same element pages"
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