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[90.235.25.56]) by smtp.gmail.com with ESMTPSA id f2-20020a2eb5a2000000b0029474e94ac6sm1272716ljn.12.2023.02.28.08.42.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Feb 2023 08:42:45 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 28 Feb 2023 17:42:43 +0100 To: lsf-pc@lists.linux-foundation.org Cc: linux-mm@kvack.org, urezki@gmail.com Subject: LSFMMBPF proposal [MM]: Eliminate vmap/vmalloc lock contention Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Stat-Signature: 95mq891w7okrkxxcjgdqugz4emfh66t9 X-Rspam-User: X-Rspamd-Queue-Id: C82D34001B X-Rspamd-Server: rspam06 X-HE-Tag: 1677602567-333360 X-HE-Meta: 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 GAzHenzP G1DTtHuYGXqIp2KXrT/9GtyQQeCMIzfNAsIf2mx0+cSs57s4E2wBAq2iZOe7q6K8cmBIoUrZIGHE8gBsVxnciuKBD3ty6oFRNLOlaRVinlGMVmVgJ2C84OZA5jD01EoJdZWSYgXSjNudFsBPt2xKGhBXCu04pfoQKvQnD1WGuGIH1irC1lzg2dMrG7hV6/Cz/fk4nDDQMDCQMfBo8X7ErWolpFFVwn37o2jwR8LjFLRYMr9CJvbEwqK74zfajSZ7U45u/wcTt33oA64k5nrgdsZI7N34LmPdUgAvX+pxPeLctiay9H2Q7QKSIooLOE4oDJ/Uad48GnuL2ssA+m9+TQD3YjEgsNipPGDKt0kmgHzHKmtTKpSmL+4fkCMzdeatsEcfEW24I5eS3waZFvcoyglKRyO0G24U6QB7HgUFa/jv7wrpmWpiMAIVQf2lq7DmoB8tP X-Bogosity: Ham, tests=bogofilter, spamicity=0.000009, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, LSF. Title: Introduce a per-cpu-vmap-cache to eliminate a vmap lock contention Description: Currently the vmap code is not scaled to number of CPU cores in a system because a global vmap space is protected by a single spinlock. Such approach has a clear bottleneck if many CPUs simultaneously access to one resource. In this talk i would like to describe a drawback, show some data related to contentions and places where those occur in a code. Apart of that i would like to share ideas how to eliminate it providing a few approaches and compare them. Requirements: * It should be a per-cpu approach; * Search of freed ptrs should not interfere with other freeing(as much as we can); * - offload allocated areas(buzy ones) per-cpu; * Cache ready sized objects or merge them into one big per-cpu-space(split on demand); * Lazily-freed areas either drained per-cpu individually or by one CPU for all; * Prefetch a fixed size in front and allocate per-cpu Goals: * Implement a per-cpu way of allocation to eliminate a contention. Thanks! -- Uladzislau Rezki