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bh=ZPZY3FkQTU5PcHvi/xKbNCo5wtFX4+klrwWTiGiGKKY=; b=QRPsVr1ql3IDuzeX0NDvrOV3XqE/uVfcC9hhiQanX/q8uEOGIYjSjRBn/xvLFyu6tt3nYk o6izVI1LSpJ6l5yrivgXO5fZ4zCU8Kp3ZIA5c9Mnv+HKAe9fM0fHE00FnHZXYXlFbnCAqJ CCKQndaZGZTrBd0sMK+TiO7/z939sKU= 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 E27F513357; Tue, 17 Jan 2023 15:57:40 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id UwP7NnTFxmNSXQAAMHmgww (envelope-from ); Tue, 17 Jan 2023 15:57:40 +0000 Date: Tue, 17 Jan 2023 16:57:40 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 39/41] kernel/fork: throttle call_rcu() calls in vm_area_free Message-ID: References: <20230109205336.3665937-1-surenb@google.com> <20230109205336.3665937-40-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230109205336.3665937-40-surenb@google.com> X-Rspamd-Queue-Id: 7470710001A X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: t3jnk7xusartmgimnz8k8kcnicc14hux X-HE-Tag: 1673971062-615666 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000018, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon 09-01-23 12:53:34, Suren Baghdasaryan wrote: > call_rcu() can take a long time when callback offloading is enabled. > Its use in the vm_area_free can cause regressions in the exit path when > multiple VMAs are being freed. What kind of regressions. > To minimize that impact, place VMAs into > a list and free them in groups using one call_rcu() call per group. Please add some data to justify this additional complexity. -- Michal Hocko SUSE Labs