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Mon, 02 Mar 2026 11:43:14 -0800 (PST) Date: Mon, 2 Mar 2026 14:43:11 -0500 From: Johannes Weiner To: Jianyue Wu Cc: akpm@linux-foundation.org, shakeel.butt@linux.dev, mhocko@kernel.org, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, inwardvessel@gmail.com Subject: Re: [PATCH v4 1/1] mm: optimize stat output for 11% sys time reduce Message-ID: References: <20260122114242.72139-1-wujianyue000@gmail.com> <20260123150108.43443-1-wujianyue000@gmail.com> <20260123150108.43443-2-wujianyue000@gmail.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260123150108.43443-2-wujianyue000@gmail.com> On Fri, Jan 23, 2026 at 11:01:08PM +0800, Jianyue Wu wrote: > +void memcg_seq_buf_print_stat(struct seq_buf *s, const char *prefix, > + const char *name, char sep, u64 val) > +{ > + char num_buf[MEMCG_DEC_U64_MAX_LEN + 2]; /* +2 for separator and newline */ > + int num_len; > + > + /* Embed separator at the beginning */ > + num_buf[0] = sep; > + > + /* Convert number starting at offset 1 */ > + num_len = num_to_str(num_buf + 1, sizeof(num_buf) - 2, val, 0); > + if (num_len <= 0) > + return; > + > + /* Embed newline at the end */ > + num_buf[num_len + 1] = '\n'; > + > + if (prefix && *prefix && seq_buf_puts(s, prefix)) > + return; > + if (seq_buf_puts(s, name)) > + return; > + /* Output separator, value, and newline in one call */ > + seq_buf_putmem(s, num_buf, num_len + 2); You seem to be losing the \0 somewhere. I'm getting garbage at the end of memory.stat on mm-new: [...] thp_swpout_fallback 1212 hp_swpout_fallback 1212 hp_swpout_fallback 1054 907 1278 Dropping this patch fixes the issue.