linux-kernel - Re: [PATCH] mm: io_uring: allow oom-killer from io_uring

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Date:   Fri, 4 Feb 2022 22:32:47 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, io-uring@...r.kernel.org
Subject: Re: [PATCH] mm: io_uring: allow oom-killer from io_uring_setup

On Mon, Jan 24, 2022 at 9:17 PM Shakeel Butt <shakeelb@...gle.com> wrote:
>
> On an overcommitted system which is running multiple workloads of
> varying priorities, it is preferred to trigger an oom-killer to kill a
> low priority workload than to let the high priority workload receiving
> ENOMEMs. On our memory overcommitted systems, we are seeing a lot of
> ENOMEMs instead of oom-kills because io_uring_setup callchain is using
> __GFP_NORETRY gfp flag which avoids the oom-killer. Let's remove it and
> allow the oom-killer to kill a lower priority job.
>
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>

Jens, any comments or concerns on this patch?

> ---
>  fs/io_uring.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index e54c4127422e..d9eeb202363c 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8928,10 +8928,9 @@ static void io_mem_free(void *ptr)
>
>  static void *io_mem_alloc(size_t size)
>  {
> -       gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP |
> -                               __GFP_NORETRY | __GFP_ACCOUNT;
> +       gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP;
>
> -       return (void *) __get_free_pages(gfp_flags, get_order(size));
> +       return (void *) __get_free_pages(gfp, get_order(size));
>  }
>
>  static unsigned long rings_size(unsigned sq_entries, unsigned cq_entries,
> --
> 2.35.0.rc0.227.g00780c9af4-goog
>