| Message ID | 20180530103936.17812-1-liwang@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, May 30, 2018 at 6:39 AM, Li Wang <liwang@redhat.com> wrote: > 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> Acked-by: Dan Streetman <ddstreet@ieee.org> > 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 >
On 30 May 2018 at 20:53, Dan Streetman <ddstreet@ieee.org> wrote: > On Wed, May 30, 2018 at 6:39 AM, Li Wang <liwang@redhat.com> wrote: >> 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> > > Acked-by: Dan Streetman <ddstreet@ieee.org> ping~ Any possible to merge this in kernel-4.18-rcX? My zswap test always fails on the upstream kernel.
On Mon, Jun 25, 2018 at 4:08 AM Li Wang <wangli.ahau@gmail.com> wrote: > > On 30 May 2018 at 20:53, Dan Streetman <ddstreet@ieee.org> wrote: > > On Wed, May 30, 2018 at 6:39 AM, Li Wang <liwang@redhat.com> wrote: > >> 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> > > > > Acked-by: Dan Streetman <ddstreet@ieee.org> > > ping~ > > Any possible to merge this in kernel-4.18-rcX? My zswap test always > fails on the upstream kernel. cc'ing Andrew as he may have missed this. > > > -- > Regards, > Li Wang > Email: wangli.ahau@gmail.com
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 */
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(+)