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From: Shakeel Butt To: Jianyue Wu Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm: optimize stat output for 11% sys time reduce Message-ID: References: <20260110042249.31960-1-jianyuew@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260110042249.31960-1-jianyuew@nvidia.com> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: q86o9fke3i968w5qeut98n9wtedbkbns X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 0E1061C0009 X-Rspam-User: X-HE-Tag: 1768264196-985144 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: On Sat, Jan 10, 2026 at 12:22:49PM +0800, Jianyue Wu wrote: > From: Jianyue Wu > > Replace seq_printf/seq_buf_printf with lightweight helpers to avoid > printf parsing in memcg stats output. > > Key changes: > - Add memcg_seq_put_name_val() for seq_file "name value\n" formatting > - Add memcg_seq_buf_put_name_val() for seq_buf "name value\n" formatting > - Update __memory_events_show(), swap_events_show(), > memory_stat_format(), memory_numa_stat_show(), and related helpers > - Introduce local variables to improve readability and reduce line length > > Performance: > - 1M reads of memory.stat+memory.numa_stat > - Before: real 0m9.663s, user 0m4.840s, sys 0m4.823s > - After: real 0m9.051s, user 0m4.775s, sys 0m4.275s (~11.4% sys drop) > > Tests: > - Script: > for ((i=1; i<=1000000; i++)); do > : > /dev/null < /sys/fs/cgroup/memory.stat > : > /dev/null < /sys/fs/cgroup/memory.numa_stat > done > > Signed-off-by: Jianyue Wu With a nit below, you can add: Acked-by: Shakeel Butt > > +/* Max 2^64 - 1 = 18446744073709551615 (20 digits) */ > +#define MEMCG_DEC_U64_MAX_LEN 20 > + > +static inline void memcg_seq_put_name_val(struct seq_file *m, const char *name, > + u64 val) > +{ > + seq_puts(m, name); > + /* need a space between name and value */ > + seq_put_decimal_ull(m, " ", val); > + seq_putc(m, '\n'); > +} > + > +static inline void memcg_seq_buf_put_name_val(struct seq_buf *s, > + const char *name, u64 val) > +{ > + char num_buf[MEMCG_DEC_U64_MAX_LEN]; > + int num_len; > + > + num_len = num_to_str(num_buf, sizeof(num_buf), val, 0); > + if (num_len <= 0) > + return; > + > + if (seq_buf_puts(s, name)) > + return; > + if (seq_buf_putc(s, ' ')) > + return; > + if (seq_buf_putmem(s, num_buf, num_len)) > + return; > + seq_buf_putc(s, '\n'); > +} Move the above functions to memcontrol.c and add documentation for them.