linux-kernel - Re: bisected bd4c82c22c367e is the first bad commit (was [Bug 198617] New: zswap causing random applications to crash)

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Date:   Mon, 5 Feb 2018 10:37:58 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     huang ying <huang.ying.caritas@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Huang, Ying" <ying.huang@...el.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Minchan Kim <minchan@...nel.org>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: bisected bd4c82c22c367e is the first bad commit (was [Bug
 198617] New: zswap causing random applications to crash)

Hi,

On (02/04/18 22:21), huang ying wrote:
[..]
> >> After disabling zswap no crashes at all.
> >>
> >> /etc/systemd/swap.conf
> >> zswap_enabled=1
> >> zswap_compressor=lz4      # lzo lz4
> >> zswap_max_pool_percent=25 # 1-99
> >> zswap_zpool=zbud          # zbud z3fold
> >
[..]
> Can you give me some detailed steps to reproduce this?  Like the
> kernel configuration file, swap configuration, etc.  Any kernel
> WARNING during testing?  Can you reproduce this with a real swap
> device instead of zswap?

No warnings (at least no warnings with my .config). Tested it only with
zram based swap (I'm running swap-less x86 systems, so zram is the easiest
way). It seems it's THP + frontswap that makes things unstable, rather
than THP + swap.

Kernel zswap boot params:
zswap.enabled=1 zswap.compressor=lz4 zswap.max_pool_percent=10 zswap.zpool=zbud

Then I add a 4G zram swap and run a silly memory hogger. I don't think
you'll have any problems reproducing it, but just in case I attached my
.config

	-ss

View attachment ".config" of type "text/plain" (91885 bytes)