linux-kernel - Re: [PATCHv2 0/4] zsmalloc: make zspage chain size configurable

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Date:   Sat, 14 Jan 2023 13:34:25 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv2 0/4] zsmalloc: make zspage chain size configurable

On 01/14/23 16:08, Sergey Senozhatsky wrote:
> On (23/01/13 11:57), Mike Kravetz wrote:
> > Hi Sergey,
> > 
> > The following BUG shows up after this series in linux-next.  I can easily
> > recreate by doing the following:
> > 
> > # echo large_value > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> > where 'large_value' is a so big that there could never possibly be that
> > many 2MB huge pages in the system.
> 
> I get migration warnins with the zsmalloc series reverted.
> I guess the problem is somewhere else. Can you double check
> on you side?

I did the following:

- Start with clean v6.2-rc3
  Perform echo, did not see issue

- Applied your 5 patches (includes the zsmalloc: turn chain size config option
  into UL constant patch).  Took default value for ZSMALLOC_CHAIN_SIZE of 8.
  Performed echo, recreated issue.

- Changed ZSMALLOC_CHAIN_SIZE to 1.
  Perform echo, did not see issue

I have not looked into the details of your patches or elsewhere.  Just thought
it might be related to your series because of the above.  And, since your
series was fresh in your mind this may trigger some thought/explanation.

It is certainly possible that root cause could be elsewhere and your series is
just exposing that.  I can take a closer look on Monday.

Thanks,
-- 
Mike Kravetz