linux-kernel - Re: [PATCH] zram_drv: add __GFP_NOWARN flag on call to zs

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Message-ID: <CAJrd-Ushm_t6voCEuTpx=Y9cms2QsRPvjkO-JAdLcwcedZ3k-A@mail.gmail.com>
Date:   Wed, 30 Mar 2022 18:11:46 +0900
From:   Jaewon Kim <jaewon31.kim@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Jaewon Kim <jaewon31.kim@...sung.com>, minchan@...nel.org,
        ngupta@...are.org, senozhatsky@...omium.org,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, s.suk@...sung.com
Subject: Re: [PATCH] zram_drv: add __GFP_NOWARN flag on call to zs_malloc

2022년 3월 30일 (수) 오후 5:49, Michal Hocko <mhocko@...e.com>님이 작성:
>
> On Wed 30-03-22 10:06:18, Michal Hocko wrote:
> > On Wed 30-03-22 14:25:02, Jaewon Kim wrote:
> > > The page allocation with GFP_NOIO may fail. And zram can handle this
> > > allocation failure. We do not need to print log for this.
> >
> > GFP_NOIO doesn't have any special meaning wrt to failures. zram
> > allocates from the memory reclaim context which is a bad design IMHO.
>
> Btw. I forgot to mention that GFP_NOIO doesn't have any different
> meaning than GFP_KERNEL from this (PF_MEMALLOC) allocation context
> because this request will never perform a reclaim.

Thank you for reply

Yes it was kswapd with PF_MEMALLOC, but I thought this zs_malloc could
fail on direct reclaim context.

I think zram is gracefully handling this ENOMEM situation, it actually
accounts the failed count as zram stats.
The failed page will be tried to swap out again later.

Yes I need to look into more about this memory shortage.
But I thought there were too many ALLOC_HADER requests in a short
time, and I want to see other
allocation failure logs like one with GFP_ATOMIC instead of this
zs_malloc failure log.

> --
> Michal Hocko
> SUSE Labs