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Date: Wed, 5 Jun 2024 00:17:47 +0200
From: Erhard Furtner <erhard_f@mailbox.org>
To: Yu Zhao <yuzhao@google.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 linuxppc-dev@lists.ozlabs.org, Johannes Weiner <hannes@cmpxchg.org>, Nhat
 Pham <nphamcs@gmail.com>, Chengming Zhou <chengming.zhou@linux.dev>, Sergey
 Senozhatsky <senozhatsky@chromium.org>, Minchan Kim <minchan@kernel.org>,
 Yosry Ahmed <yosryahmed@google.com>
Subject: Re: kswapd0: page allocation failure: order:0,
 mode:0x820(GFP_ATOMIC), nodemask=(null),cpuset=/,mems_allowed=0 (Kernel
 v6.5.9, 32bit ppc)
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On Tue, 4 Jun 2024 11:18:25 -0600
Yu Zhao <yuzhao@google.com> wrote:

> Hi Erhard,
> 
> If it's not too much trouble, could you "grep nr_zspages /proc/vmstat"
> on kernels before and after the bad commit? It'd be great if you could
> run the grep command right before the OOM kills.
> 
> The overall internal fragmentation of multiple zsmalloc pools might be
> higher than a single one. I suspect this might be the cause.
> 
> Thank you.

I used watch -n1 'grep nr_zspages /proc/vmstat' to get the readings and repeated this 3 times to check whether the reported values differ much.

Bad commit was b8cf32dc6e8c75b712cbf638e0fd210101c22f17 "mm: zswap: multiple zpools support", next commit in git log after the bad one would be 42c06a0e8ebe95b81e5fb41c6556ff22d9255b0c "mm: kill frontswap".

With this kernel I got 2440, 2337, 3245 as nr_zspages and the kswapd0: page allocation error.

Commit in git log before the bad one would be bfaa4a0ce1bbc1b2b67de7e4c2e1679495f7b905 "scsi: gvp11: Remove unused
gvp11_setup() function".

With this kernel I got 25537, 11321, 16087 as nr_zspages and the OOM reaper.

Tomorrow I could also check the .config changes Vlastimil suggested (CONFIG_SLAB_MERGE_DEFAULT=y, no CONFIG_RANDOM_KMALLOC_CACHES) and report back if that's of interest.

Regards,
Erhard