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bh=bbHjv8f4G8yVHoUHU7VHjKcNPXbqT19MIbDP7lW2Ypw=; b=AH95UKrzJ1Zliz+zgEejEfNeedAWYpcTW4dL6WRZ4YuKSDpRhdJmRAgphp/BNidqkNZSdS n3efqyXjohG1QoWVwbLTiaMNcMXlfZ2q2fSgmImd3a+aspnHBzE78VhzTqh/A/s5Dz0f4s gTF0p1am8yTAw6I0wEVbjPDtyvfku3M= 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 98C9C1358A; Wed, 11 Jan 2023 18:03:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id /ULTJNT5vmMBBgAAMHmgww (envelope-from ); Wed, 11 Jan 2023 18:03:00 +0000 Date: Wed, 11 Jan 2023 19:02:59 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: David Laight , Ingo Molnar , "michel@lespinasse.org" , "joelaf@google.com" , "songliubraving@fb.com" , "leewalsh@google.com" , "david@redhat.com" , "peterz@infradead.org" , "bigeasy@linutronix.de" , "peterx@redhat.com" , "dhowells@redhat.com" , "linux-mm@kvack.org" , "edumazet@google.com" , "jglisse@google.com" , "punit.agrawal@bytedance.com" , "arjunroy@google.com" , "minchan@google.com" , "x86@kernel.org" , "hughd@google.com" , "willy@infradead.org" , "gurua@google.com" , "laurent.dufour@fr.ibm.com" , "linux-arm-kernel@lists.infradead.org" , "rientjes@google.com" , "axelrasmussen@google.com" , "kernel-team@android.com" , "soheil@google.com" , "paulmck@kernel.org" , "jannh@google.com" , "liam.howlett@oracle.com" , "shakeelb@google.com" , "luto@kernel.org" , "gthelen@google.com" , "ldufour@linux.ibm.com" , "vbabka@suse.cz" , "posk@google.com" , "lstoakes@gmail.com" , "peterjung1337@gmail.com" , "linuxppc-dev@lists.ozlabs.org" , "kent.overstreet@linux.dev" , "hughlynch@google.com" , "linux-kernel@vger.kernel.org" , "hannes@cmpxchg.org" , "akpm@linux-foundation.org" , "tatashin@google.com" Subject: Re: [PATCH 08/41] mm: introduce CONFIG_PER_VMA_LOCK Message-ID: References: <20230111001331.cxdeh52vvta6ok2p@offworld> <6be809f5554a4faaa22c287ba4224bd0@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BBCCBA0009 X-Rspam-User: X-Stat-Signature: r8f7ob387gwowz4esi6w7g7uye9wwaxo X-HE-Tag: 1673460194-305985 X-HE-Meta: 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 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 11-01-23 09:49:08, Suren Baghdasaryan wrote: > On Wed, Jan 11, 2023 at 9:37 AM Michal Hocko wrote: > > > > On Wed 11-01-23 09:04:41, Suren Baghdasaryan wrote: > > > On Wed, Jan 11, 2023 at 8:44 AM Michal Hocko wrote: > > > > > > > > On Wed 11-01-23 08:28:49, Suren Baghdasaryan wrote: > > > > [...] > > > > > Anyhow. Sounds like the overhead of the current design is small enough > > > > > to remove CONFIG_PER_VMA_LOCK and let it depend only on architecture > > > > > support? > > > > > > > > Yes. Further optimizations can be done on top. Let's not over optimize > > > > at this stage. > > > > > > Sure, I won't optimize any further. > > > Just to expand on your question. Original design would be problematic > > > for embedded systems like Android. It notoriously has a high number of > > > VMAs due to anonymous VMAs being named, which prevents them from > > > merging. > > > > What is the usual number of VMAs in that environment? > > I've seen some games which had over 4000 VMAs but that's on the upper > side. In my calculations I used 40000 VMAs as a ballpark number and > rough calculations before size optimization would increase memory > consumption by ~2M (depending on the lock placement in vm_area_struct > it would vary a bit). In Android, the performance team flags any > change that exceeds 500KB, so it would raise questions. Thanks, that is a useful information! This is just slightly off-topic but I ak wondering how much memory those vma names consume. Are there that many unique names or they just happen to be alternating so that neighboring ones tend to be different. -- Michal Hocko SUSE Labs