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| author | zhouxianrong <zhouxianrong@huawei.com> | 2017-02-24 14:59:27 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-24 17:46:56 -0800 |
| commit | 8e19d540d107ee897eb9a874844060c94e2376c0 (patch) | |
| tree | a268e406f52137cf0f81150c8f27b0c9100c6bfb /Documentation | |
| parent | 517663edd6b5d2a822469885994f34e092e2cf9f (diff) | |
| download | lwn-8e19d540d107ee897eb9a874844060c94e2376c0.tar.gz lwn-8e19d540d107ee897eb9a874844060c94e2376c0.zip | |
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 <zhouxianrong@huawei.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/blockdev/zram.txt | 6 |
1 files changed, 3 insertions, 3 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 |