Re: [PATCH v2 1/2] memcg: use seq_buf_do_printk() with mem_cgroup_print_oom_meminfo()

From: Muchun Song <muchun.song@linux.dev>
To: Yosry Ahmed <yosryahmed@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Shakeel Butt <shakeelb@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Petr Mladek <pmladek@suse.com>, Chris Li <chrisl@kernel.org>,
	cgroups@vger.kernel.org,
	Linux Memory Management List <linux-mm@kvack.org>,
	linux-kernel@vger.kernel.org, Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH v2 1/2] memcg: use seq_buf_do_printk() with mem_cgroup_print_oom_meminfo()
Date: Fri, 5 May 2023 11:46:10 +0800	[thread overview]
Message-ID: <5BE37965-9A20-4743-A2BC-E407D89C53D1@linux.dev> (raw)
In-Reply-To: <20230428132406.2540811-2-yosryahmed@google.com>

> On Apr 28, 2023, at 21:24, Yosry Ahmed <yosryahmed@google.com> 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@google.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

Reviewed-by: Muchun Song <songmuchun@bytedance.com>

Thanks.