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[124.209.188.1]) by smtp.gmail.com with ESMTPSA id m21-20020a62a215000000b0063f33e216dasm8082880pff.96.2023.04.26.17.45.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Apr 2023 17:45:30 -0700 (PDT) Date: Thu, 27 Apr 2023 09:45:25 +0900 From: Sergey Senozhatsky To: Yosry Ahmed Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Andrew Morton , Muchun Song , Sergey Senozhatsky , Steven Rostedt , Petr Mladek , Chris Li , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] memcg: use seq_buf_do_printk() with mem_cgroup_print_oom_meminfo() Message-ID: <20230427004525.GE1496740@google.com> References: <20230426133919.1342942-1-yosryahmed@google.com> <20230426133919.1342942-2-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230426133919.1342942-2-yosryahmed@google.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 5BC8F4000A X-Stat-Signature: 38x5kmrfkk7eep4ebwbho5ytb96zscrh X-HE-Tag: 1682556332-8693 X-HE-Meta: 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 sYe9i9cb h2Q3/sG4PzH41XnUbjCxGsWYIs4jXljkrJfOaD+Eq8l7y3lujxwSesMMBDUREEEaNPXRU9hMfM3djwQx5DSBg7JpRe9TP1BngPALVNkIR4BdEivAdiVwLg+zhXorVdper/0tvHhN06iLtIPzHC88ADbf8ejQQNGduklROb/dXQsIAMsKdW3k6AHoGrWFYXDbJYlEzYoKg4aUvB2V64v3i06eS7jjLl8HoQfR3EglsMWsSdG2DXlo6m8CGmazTIStboZdIWPrA3rcMas+jefPVAnd5IbqNyp3lZ0tNF23Ex5pryMji/d9cNaAJAlws+Omu7V17r9eXkOe9llc4S5Yxjks9cJXYhQi+6XwfiuhQPlZrvdRI7sdQn6dxKg/cPb3INLVhkyvPn5gJgjHFL4HYFmdeIHfs2V06SaZ9OmWA2jzd6IUot387hdGV29QabRhTIHg+hByuAZjWqaVDbTvYbVkUyg75VtsqLs1Q X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 FWIW, Reviewed-by: Sergey Senozhatsky