Messages in this thread Patch in this message | | | From | Li Wang <> | Subject | [PATCH v2] zswap: re-check zswap_is_full after do zswap_shrink | Date | Wed, 30 May 2018 18:39:36 +0800 |
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The '/sys/../zswap/stored_pages:' keep raising in zswap test with "zswap.max_pool_percent=0" parameter. But theoretically, it should not compress or store pages any more since there is no space in compressed pool.
Reproduce steps: 1. Boot kernel with "zswap.enabled=1" 2. Set the max_pool_percent to 0 # echo 0 > /sys/module/zswap/parameters/max_pool_percent 3. Do memory stress test to see if some pages have been compressed # stress --vm 1 --vm-bytes $mem_available"M" --timeout 60s 4. Watching the 'stored_pages' number increasing or not
The root cause is: When zswap_max_pool_percent is setting to 0 via kernel parameter, the zswap_is_full() will always return true to do zswap_shrink(). But if the shinking is able to reclain a page successful, then proceeds to compress/store another page, so the value of stored_pages will keep changing.
To solve the issue, this patch adds zswap_is_full() check again after zswap_shrink() to make sure it's now under the max_pool_percent, and not to compress/store if reach its limitaion.
Signed-off-by: Li Wang <liwang@redhat.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: Huang Ying <huang.ying.caritas@gmail.com> Cc: Yu Zhao <yuzhao@google.com> --- mm/zswap.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/mm/zswap.c b/mm/zswap.c index 61a5c41..fd320c3 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1026,6 +1026,15 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, ret = -ENOMEM; goto reject; } + + /* A second zswap_is_full() check after + * zswap_shrink() to make sure it's now + * under the max_pool_percent + */ + if (zswap_is_full()) { + ret = -ENOMEM; + goto reject; + } } /* allocate entry */ -- 2.9.5
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