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]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6E1DECAAD4 for ; Wed, 31 Aug 2022 15:37:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3B2FE6B0071; Wed, 31 Aug 2022 11:37:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 33B748D0001; Wed, 31 Aug 2022 11:37:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1DBEF6B0073; Wed, 31 Aug 2022 11:37:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 08F9F6B0071 for ; Wed, 31 Aug 2022 11:37:27 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id CBBA714055B for ; Wed, 31 Aug 2022 15:37:26 +0000 (UTC) X-FDA: 79860292092.07.1D4A66D Received: from mail-yw1-f174.google.com (mail-yw1-f174.google.com [209.85.128.174]) by imf09.hostedemail.com (Postfix) with ESMTP id 83E6A14004C for ; Wed, 31 Aug 2022 15:37:26 +0000 (UTC) Received: by mail-yw1-f174.google.com with SMTP id 00721157ae682-3378303138bso310805787b3.9 for ; Wed, 31 Aug 2022 08:37:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=Z5bWT124P9msiKtHJxXWtamGxGE9nU7NFSbNkXeVir4=; b=q4yt7LQZaKZTdzRnqOfBDWuxDUawgahY2C4+8NClZrlVWpZiq8b8wuUtt2FXanHGEc GKUHZeMZM5jPluxM3gpqfRkq+ZEpQLG+BNvz98YUVO6qqcwbNq/QfwpxfY1bBqJ/PbUe qN9rURlcwiX2U8yaFrSKUwROmM3LF8ndCfS6j0AHC4HsQL8z7s2/MCCQMTRvX3Ne6rDh NX1iVO84IZTdrxORhVNpFjbUB389eDGDLX9acAC39/jQL/Xkcw+zdEhsbVQSkIB5PGSl 3MgCLAYUQZJEhdAOCDXe/UR2KtUxqwQZuMK/LjLdJHtYQZbxs0yHQAWgM70EmS5KjdKg raEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=Z5bWT124P9msiKtHJxXWtamGxGE9nU7NFSbNkXeVir4=; b=M5JzBbn6mZfJIW2+KtuEzYxEfdGTqqtpIxRFz/jPjhDgBdNcFWebDlKWLAFi9BXxqa LWLUME/tPfEZJ+C5+HwWAbm6vD+qe0scGReXFGhGgV/9vupzHAXG0d80/Ys2EFSwRoJ/ zi62sFI1OozAFBXnizyO4gmmFaQm9n2UJdjjlBGxMCmf4F1ffpSSsjmdXQCz0ky0e8NW 1yWlD8bfcSXJhurHbei+Tt3t0wICSYVLRTJe3W4eljK+ocTLjaw4ueauVG3URYwtpU3E bILW/Jw53XgCd0GIbMBmG/YxrNY2CJi8WNaSqaK8KWpbhPV3CgBNC5L7YNchMe9Moj/b jEEg== X-Gm-Message-State: ACgBeo1h8DS65tdXsSlCX6PJljBmpfDlvTBK1u+cCi1q+Dxj1gswRwv0 fpe8d6K/RuUwM0p7EvqUWauGMVUENuEV+jrjKolcJw== X-Google-Smtp-Source: AA6agR4eyfrVHwFKMQTAM4+K85p4B7I6c+zSy9tLGnKDo68fc8kY3s9yyQtJtbnPccojelXd5+hkkFEpEU7+woAq0vg= X-Received: by 2002:a81:7784:0:b0:33d:ca62:45f5 with SMTP id s126-20020a817784000000b0033dca6245f5mr18452862ywc.180.1661960245620; Wed, 31 Aug 2022 08:37:25 -0700 (PDT) MIME-Version: 1.0 References: <20220830214919.53220-1-surenb@google.com> <20220830214919.53220-4-surenb@google.com> <20220831100249.f2o27ri7ho4ma3pe@suse.de> In-Reply-To: <20220831100249.f2o27ri7ho4ma3pe@suse.de> From: Suren Baghdasaryan Date: Wed, 31 Aug 2022 08:37:14 -0700 Message-ID: Subject: Re: [RFC PATCH 03/30] Lazy percpu counters To: Mel Gorman Cc: Andrew Morton , Kent Overstreet , Michal Hocko , Vlastimil Babka , Johannes Weiner , Roman Gushchin , Davidlohr Bueso , Matthew Wilcox , "Liam R. Howlett" , David Vernet , Peter Zijlstra , Juri Lelli , Laurent Dufour , Peter Xu , David Hildenbrand , Jens Axboe , mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, changbin.du@intel.com, ytcoode@gmail.com, Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Benjamin Segall , Daniel Bristot de Oliveira , Valentin Schneider , Christopher Lameter , Pekka Enberg , Joonsoo Kim , 42.hyeyoo@gmail.com, Alexander Potapenko , Marco Elver , dvyukov@google.com, Shakeel Butt , Muchun Song , arnd@arndb.de, jbaron@akamai.com, David Rientjes , Minchan Kim , Kalesh Singh , kernel-team , linux-mm , iommu@lists.linux.dev, kasan-dev@googlegroups.com, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-modules@vger.kernel.org, LKML Content-Type: text/plain; charset="UTF-8" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661960246; 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=Z5bWT124P9msiKtHJxXWtamGxGE9nU7NFSbNkXeVir4=; b=ZyfSnL7iIDRViEkzbH8PBTsioIC2O2ID7aq+MubhCnR17hpE+5AG/jotAwf9BFkSRbGVRD tadmC1nDxH4/4A2jguhsmKL80D9UIycIo6WlyfgWXoQqW75WdZMf9xXJltc8hnp58pF1ed yoYTAkMAmXIY5qNJAGXKd4P85ALrdI4= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=q4yt7LQZ; spf=pass (imf09.hostedemail.com: domain of surenb@google.com designates 209.85.128.174 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661960246; a=rsa-sha256; cv=none; b=vqydP+l+ZmoaEer10GX93xfWnHwRb+rIp88GnkVv8fIHPtqrDeVS701GwwddHl8s0WNm2C Lwgx89fe7o1VOwZxWfMInx1G5yB0p+9EA34gY0NRmKmDVkyhV+UNFO9Ncm2KrSOqnnz9Q7 bT+7AqAjRRvgc/OxvPW5pB0fmve+uFw= X-Rspamd-Queue-Id: 83E6A14004C Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=q4yt7LQZ; spf=pass (imf09.hostedemail.com: domain of surenb@google.com designates 209.85.128.174 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspam-User: X-Rspamd-Server: rspam10 X-Stat-Signature: jkbt5ubtxax1hrgnewzx7hsarzeuh7a1 X-HE-Tag: 1661960246-144615 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 Wed, Aug 31, 2022 at 3:02 AM Mel Gorman wrote: > > On Tue, Aug 30, 2022 at 02:48:52PM -0700, Suren Baghdasaryan wrote: > > From: Kent Overstreet > > > > This patch adds lib/lazy-percpu-counter.c, which implements counters > > that start out as atomics, but lazily switch to percpu mode if the > > update rate crosses some threshold (arbitrarily set at 256 per second). > > > > Signed-off-by: Kent Overstreet > > Why not use percpu_counter? It has a per-cpu counter that is synchronised > when a batch threshold (default 32) is exceeded and can explicitly sync > the counters when required assuming the synchronised count is only needed > when reading debugfs. The intent is to use atomic counters for places that are not updated very often. This would save memory required for the counters. Originally I had a config option to choose which counter type to use but with lazy counters we sacrifice memory for performance only when needed while keeping the other counters small. > > -- > Mel Gorman > SUSE Labs