From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 79A7C2D47EF for ; Thu, 8 Jan 2026 22:50:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767912652; cv=none; b=LUnEuUwDUKWIJH4Yf49hvdXN3rzyvJO20NZTnlhNPBbaoqGt5blyB5oSvUCcB4O50B4ByKQ2/HD0pqkzf0G86Tn1nH/469nDASaBl2y4s4boLagX+F3vRGHybNnntXIwT7jL7PdZ8Fgj7e0lZjyZDzq9vZOUlPACEV/qDE2wol8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767912652; c=relaxed/simple; bh=ZOD+3sEuARst8J/6jQKUAN+c3CEyZm47JpYqTHAT2i8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=L/PKl39byJ5DMnXjlCI8F2Qt1y9/ueVnxqDXx4chGGFtBVy2ASc1ZvPwKxg8C1M+MZseD51zPEMh/VACq2wLUUGYhgoyf4gAbmfnAhwW/V9xezcXUC042Svtuh8i/9V4VjGeHjIVpisqTyaKNnDox+yt+TFzTzeeP5eVC9lwZvM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=S8lNzgxB; arc=none smtp.client-ip=95.215.58.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="S8lNzgxB" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1767912638; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=GiutodSCryP8xE+zUXAHFxoi+kF4AieFcdf6dqFfuM0=; b=S8lNzgxBrs+O14O5zBi0n1LeqQ3o6mRMOpQFXNjmjrDuPUR8o4Lk2u2r/b5XeYJL28srVA Wjh00dH7rAOs2GUKLeyMUYQ2OiscoskiSuC6vnxlcBwg2GpQOyBjqpof4YlXaZutHTDQML uVVRZuzVbru4j/zUIx76MVtaUTssF04= From: Roman Gushchin To: Andrew Morton Cc: Jianyue Wu , jianyuew@nvidia.com, hannes@cmpxchg.org, mhocko@kernel.org, shakeel.butt@linux.dev, muchun.song@linux.dev, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: optimize stat output for 11% sys time reduce In-Reply-To: <20260108111027.172f19a9a86667e8e0142042@linux-foundation.org> (Andrew Morton's message of "Thu, 8 Jan 2026 11:10:27 -0800") References: <20260108093741.212333-1-jianyuew@nvidia.com> <20260108111027.172f19a9a86667e8e0142042@linux-foundation.org> Date: Thu, 08 Jan 2026 22:49:55 +0000 Message-ID: <7ia45x9bhg8c.fsf@castle.c.googlers.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT Andrew Morton writes: > On Thu, 8 Jan 2026 17:37:29 +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 >> >> 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 >> > > I suspect there are workloads which read these files frequently. > > I'd be interested in learning "how frequently". Perhaps > ascii-through-sysfs simply isn't an appropriate API for this data? We just got a bpf interface for this data merged, exactly to speed things up: commit 99430ab8b804 ("mm: introduce BPF kfuncs to access memcg statistics and events") in bpf-next.