From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 81F0410F6FA1 for ; Wed, 1 Apr 2026 14:39:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ED5346B008A; Wed, 1 Apr 2026 10:39:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EACF96B008C; Wed, 1 Apr 2026 10:39:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DE9D56B0092; Wed, 1 Apr 2026 10:39:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id CC02E6B008A for ; Wed, 1 Apr 2026 10:39:43 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 7C8328C6E8 for ; Wed, 1 Apr 2026 14:39:43 +0000 (UTC) X-FDA: 84610245846.14.62B712F Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) by imf14.hostedemail.com (Postfix) with ESMTP id E2DD2100008 for ; Wed, 1 Apr 2026 14:39:41 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=debian.org header.s=smtpauto.stravinsky header.b=MbiMBtFd ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1775054382; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=kz9xdstn7TOu/urPKjmoJJTfAwSQj9gbccp6E1YBcZQ=; b=y9lr74uq3/CevVWGntpaOXoeUDaOCgqzRDhhbrRtilmXgM834XDoKbfMKJHhqR9qSxUWwH T38zN3y+ZtaaqKlFIJR9i4Yq6rosfhpEQkpphSAMFT107cpiJ7++Ovg/5pVwEvZeNWehvb VRGtlTndyVnRrA6gfa0qYAwJJBQdem0= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1775054382; a=rsa-sha256; cv=none; b=VaKqZo9N2uzvQuv8FVIOPFIZcCnkUaV/zt7eWj4glc7d+9QxN3hq6wC9Jhx/g/tVI8k8Cr VifxpvWhV71VI9MN3XaTaEVtdqE+VwMcL55z9fNcI1E5WHbWBtM7TslFKB+aRxbTcoraPb w5ACL52iXbCpAAcmJdjersAWRv8AFq0= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=debian.org header.s=smtpauto.stravinsky header.b=MbiMBtFd; dmarc=none; spf=none (imf14.hostedemail.com: domain of leitao@debian.org has no SPF policy when checking 82.195.75.108) smtp.mailfrom=leitao@debian.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=kz9xdstn7TOu/urPKjmoJJTfAwSQj9gbccp6E1YBcZQ=; b=MbiMBtFd8sy6bcBTxzwXGMGp4y SLdX++76Av545JJkZ//03Vg21lujlT85vY6KO5Z855vZfxhnWaDUWgG3vcxDzZRqfo5IeGcS8AKf9 a6jNEJQggp204zXYKicDBoATturVJ2GrWdb0TN9l3DZazjFu+Ey7VIlC/keQl6VDYVJYodBsft33D DXpX8uySUXHLeALPE3lzasNYyOvJ8yf7mpXkrOdRJidWpWTwWtTO3bMbrsIeMgzuqD2L4RdF0g7EY TGcweAEORZOYQmydBCJngjoRdTrekqAXHXqgA1DYGdEnrvodj/JkVzNrwzm3prfPZ0ikMvfKiv90S q4VD+Srw==; Received: from authenticated user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1w7wjH-0033XU-0D; Wed, 01 Apr 2026 14:39:33 +0000 Date: Wed, 1 Apr 2026 07:39:28 -0700 From: Breno Leitao To: Johannes Weiner Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kas@kernel.org, shakeel.butt@linux.dev, usama.arif@linux.dev, kernel-team@meta.com Subject: Re: [PATCH] mm/vmstat: spread vmstat_update requeue across the stat interval Message-ID: References: <20260401-vmstat-v1-1-b68ce4a35055@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Debian-User: leitao X-Rspamd-Queue-Id: E2DD2100008 X-Stat-Signature: dii874bti63y9uq4brxi896rjjd5k3wg X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1775054381-501795 X-HE-Meta: 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello Johannes, On Wed, Apr 01, 2026 at 10:25:35AM -0400, Johannes Weiner wrote: > On Wed, Apr 01, 2026 at 06:57:50AM -0700, Breno Leitao wrote: > > +static unsigned long vmstat_spread_delay(void) > > +{ > > + unsigned long interval = sysctl_stat_interval; > > + unsigned int nr_cpus = num_online_cpus(); > > + > > + if (nr_cpus <= 1) > > + return round_jiffies_relative(interval); > > + > > + /* > > + * Spread per-cpu vmstat work evenly across the interval. Don't > > + * use round_jiffies_relative() here -- it would snap every CPU > > + * back to the same second boundary, defeating the spread. > > + */ > > + return interval + (interval * (smp_processor_id() % nr_cpus)) / nr_cpus; > > smp_processor_id() <= nr_cpus, so > > return interval + interval*cpu/nr_cpus > > should be equivalent, no? nr_cpus is the number of online CPUs, while smp_processor_id() is the CPU id. If you offline a CPU, then smp_processor_id() might be bigger than num_online_cpus() My goal was to linearly shift the timer and avoid creating gaps when removing certain CPUs. Thanks for the review, --breno