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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683823601; x=1686415601; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=kNp5WlKE+rMe+FP2MCodV5giQtFPoKvOIzEU8FA+LAE=; b=giMDsRHdhVVvM5mu4BSDV6anconp8+Os76EzU6to346wlA/JMvjnC6O4juc/Q0nw0+ I7eomK51gFqQ6zsBl6HZIv7HcZJidZCW2CFXzfS/1plwmRjP6OHDaGA06g/xSO1hmnHz FlpFgAqYbW1uDMmTX4VRF269mNqTNeI5cW8aH7Xa1/0P66biIeP4xUgMKQGs3XzPTzru VO8/6+wQQ27xnElCRoIzLo+wNcF8yIkaTU51BB9zOQIHBq6CDr40VgpkZRytrRhIp/Ay 1HGJOrVnEHFtjNvx8qmkhtVO1+hZfHjyPR2k/quv9+tcH7iK0dU01BdgIU8unMh2fLO5 GaFQ== X-Gm-Message-State: AC+VfDwlwjq1/ORnqhP9Rr40V6lkSBc2jCvgCWFXNn6IU70iaO5xWAm6 H1HTcJxJfhnCRNx7yxowiP8QI5jtnXyGAUsKNxQ= X-Google-Smtp-Source: ACHHUZ7Y6Hfh79Er4yK96HII3edIaQFCcYJuhwF44ORfvDWN66ZcMQq5rAWK7VPjBL8rsZQOLiXey95qJs7dQvLP42M= X-Received: by 2002:a05:6402:295:b0:50b:c6c9:2146 with SMTP id l21-20020a056402029500b0050bc6c92146mr16013403edv.24.1683823601123; Thu, 11 May 2023 09:46:41 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Uladzislau Rezki Date: Thu, 11 May 2023 18:46:29 +0200 Message-ID: Subject: Re: LSFMMBPF proposal [MM]: Eliminate vmap/vmalloc lock contention To: lsf-pc@lists.linux-foundation.org Cc: linux-mm@kvack.org, Lorenzo Stoakes Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: oha8uhujddc3sp8jquiuzribzds5dy4f X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 0287AA0014 X-HE-Tag: 1683823602-961971 X-HE-Meta: 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 V5g3TuTY TazrqEVgIahihaDsge1Es96MVt2D5XNj1O1Z5TpeX23BlFBvpBeG2HwMlARecBM32SZ6hzXfc/KmowDTnaDaB/YiT9azC31I2dkEhPiyks48gPjVLbDDYkQAmE4pooIl3n64mr7NHCWdTgmM8rAqk/51MwR0SkmPV3FHLzc2Dxw3UAMy6m5NIos/X0Zz/TYN0PvnBkYiO4+I00viL2FwaJDlb4FWMC2o0DFYbOnJtsGZ2MTzNx91nS8w2K5Ci1vhpauKJLLGKANqWu+rUA7jSY4rkS8Umqr1/0yaD7Z7NTxkIiAZQYMTik4umZMYTSdSac8E/rPVRzD7lglWDG1nL7V3a+WSWNUge7JLIH+kxq9/gLRYSJhGRdIimi6NkCmX0waZLbEOBQtSxllpcfRTjsl2cPOJKQ+PelB0j X-Bogosity: Ham, tests=bogofilter, spamicity=0.000264, 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. > Thank you for giving a time to talk about this topic on the LSFMMBPF. The slides can be accessed here: wget ftp://vps418301.ovh.net/incoming/Mitigate_a_vmalloc_lock_contention_in_SMP_env_v1.pdf There were some issues with a camera, but i was told in the end you could see me.2 Thank you again! -- Uladzislau Rezki