linux-kernel - Re: [PATCH 1/2] memcg: use seq_buf_do_printk() with mem_cgroup_print_oom

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Message-ID: <20230427004525.GE1496740@google.com>
Date:   Thu, 27 Apr 2023 09:45:25 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Muchun Song <muchun.song@...ux.dev>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Petr Mladek <pmladek@...e.com>, Chris Li <chrisl@...nel.org>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] memcg: use seq_buf_do_printk() with
 mem_cgroup_print_oom_meminfo()

On (23/04/26 13:39), Yosry Ahmed wrote:
> Currently, we format all the memcg stats into a buffer in
> mem_cgroup_print_oom_meminfo() and use pr_info() to dump it to the logs.
> However, this buffer is large in size. Although it is currently working
> as intended, ther is a dependency between the memcg stats buffer and the
> printk record size limit.
> 
> If we add more stats in the future and the buffer becomes larger than
> the printk record size limit, or if the prink record size limit is
> reduced, the logs may be truncated.
> 
> It is safer to use seq_buf_do_printk(), which will automatically break
> up the buffer at line breaks and issue small printk() calls.
> 
> Refactor the code to move the seq_buf from memory_stat_format() to its
> callers, and use seq_buf_do_printk() to print the seq_buf in
> mem_cgroup_print_oom_meminfo().
> 
> Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>

FWIW,
Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>