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From:   Dan Streetman <ddstreet@ieee.org>
Date:   Wed, 25 Jul 2018 07:29:05 -0400
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Subject: Re: [PATCH v2] zswap: re-check zswap_is_full after do zswap_shrink
To:     wangli.ahau@gmail.com, Andrew Morton <akpm@linux-foundation.org>
Cc:     Li Wang <liwang@redhat.com>, Linux-MM <linux-mm@kvack.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Seth Jennings <sjenning@redhat.com>,
        huang ying <huang.ying.caritas@gmail.com>,
        Yu Zhao <yuzhao@google.com>
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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