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bh=LhJ5sTl63kPWjdnDX0OeDaOslOG+1efqgSGhwPg2LwY=; b=OZAWOqBQsCEfpI3eFuLk7qToZKY+SYTEOk72LyofIJymzTGxX7iTneBlvSQa1EtpyTEC66 9MfOrbNbfb0xXS5YRf8l+Hc4af3UnLICdYto92i8Net2jWr6FpKUI/1z1CgqCZjGdkYx6/ JOU72i1B90DxzFoA2gmVtBFUPLmhYEs= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 58FA213585; Mon, 4 Sep 2023 15:41:11 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id jP6fEpf69WRyVAAAMHmgww (envelope-from ); Mon, 04 Sep 2023 15:41:11 +0000 Date: Mon, 4 Sep 2023 17:41:10 +0200 From: Michal Hocko To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: Yosry Ahmed , Andrew Morton , Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Ivan Babrou , Tejun Heo , Waiman Long , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 3/4] mm: memcg: let non-unified root stats flushes help unified flushes Message-ID: References: <20230831165611.2610118-1-yosryahmed@google.com> <20230831165611.2610118-4-yosryahmed@google.com> <6tne52ip62ucev7nmnim3m7fhcydnwcytyxynrlxxgaf4cbqea@r4hec425izap> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6tne52ip62ucev7nmnim3m7fhcydnwcytyxynrlxxgaf4cbqea@r4hec425izap> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 268D81C000D X-Stat-Signature: n8w5iu4yq5gtfi7u35tusb8n7pd7mqbe X-HE-Tag: 1693842072-447423 X-HE-Meta: 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 tO+H8TGa snhzovouZr6naDhMH+bCFxajC/+qZDboqZWlF2Jv4NLZSVB0I5W25KWAtQkURN5jPXpxWkfqncR0GWdfL6fGSf2QOpJA3fW2fhiSWeIhjFZHUF+5Mvi1JbvtHvE+YmtHAanX1JAnqN2uRorUeQhuyLs9jTyz1UD0+IJT4gayqIWbvATSHwKP5+CLTJUah7Ko2EpKU4c4lE+4HDftxMq2a0O4HVZx6cJHJF1Kn8U4/n0z5hyE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon 04-09-23 17:29:14, Michal Koutny wrote: > Hello. > > On Mon, Sep 04, 2023 at 04:50:15PM +0200, Michal Hocko wrote: > > I have hard time to follow why we really want/need this. Does this cause > > any observable changes to the behavior? > > Behavior change depends on how much userspace triggers the root memcg > flush, from nothing to effectively offloading flushing to userspace tasks. > (Theory^^^) > > It keeps stats_flush_threshold up to date representing global error > estimate so that error-tolerant readers may save their time and it keeps > the reasoning about the stats_flush_threshold effect simple. So it also creates an undocumented but userspace visible behavior. Something that userspace might start depending on, right? -- Michal Hocko SUSE Labs