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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1738344695; bh=uDGIYzvVvz1Yg61KexnHobDE2HMWuZriExs/LO5tQu0=; h=Date:From:To:Cc:Subject:Content-Type; b=WdPWWh6Gs5IYzBogP8z1oZBEFgaT4Idq2Vpx+z0g5hjxwUNUJQV5rEmAuVKUNmfjb onbzLBSZFrNu0y+TW+Uh6kT7hSQxVTs2SkWV6bJGS/AlY+mmwCAtJeYYuudN9dp+pj rZSGOXVmE9PDgDsmL6Dpxjog8lsyCuQMPQ17gX+QQySkNMv28OsqgMuVNQLMuoYjIG mBWMyVx5tQxBBQZ1LmTKM+SXNf7yC8zBnpz0zNZ4tj+QOg9pddGy2s+UdkX+STsSCA kZx5YuO5lEyuXRRCVYn8fQInCXFBRuvWrIk7GlXs61ExZfb3aTUCqRnl7SnaakTD6P GYphyau7P0GfQ== Date: Fri, 31 Jan 2025 09:31:32 -0800 From: Davidlohr Bueso To: Lorenzo Stoakes Cc: SeongJae Park , "Liam R. Howlett" , Andrew Morton , David Hildenbrand , Shakeel Butt , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v2 4/4] mm/madvise: remove redundant mmap_lock operations from process_madvise() Message-ID: <20250131173132.uqjwrzj7e5vx2sbv@offworld> Mail-Followup-To: Lorenzo Stoakes , SeongJae Park , "Liam R. Howlett" , Andrew Morton , David Hildenbrand , Shakeel Butt , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20250117013058.1843-1-sj@kernel.org> <20250117013058.1843-5-sj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220429 X-Rspam-User: X-Rspamd-Queue-Id: 7CB63160025 X-Rspamd-Server: rspam10 X-Stat-Signature: a5zixmiijiohpx3kfgku87o5jr3q5xh6 X-HE-Tag: 1738344699-898659 X-HE-Meta: U2FsdGVkX18txtVF3pkVb/B72hzg6Cqs22wIfnZr+CtLaPnr9i1YuYgsGqAZQ8lDFgTIxKgg7vnAI2ZSGdA1BkrxPYgqi0VI+3ayCwnBJiV40F3WFPPH/1+/uz6+Ln6P1AjYlPx/S5bERMWoGUSQNUS8S50+NWqw/qxbdX49OFoJf2C4ZAxEyaLHkUPZl8qrRE72fy1JgGvCTW8U2wunLahp2e+QzpWB2FnCmxcPuE1QzkjAJXKvSty/EYA8lMj4vslwRrUT32YyzTazb38ZYRXdnUCVHmRqkPEtwen3kKRKq601OoKITFda7GzWn4dc0KXFaPvzhJd6vR9JxJrZBgTQ2QWbp3If/iOp0PTYCY+RFQfkU1uLHmOr/OzN+0/UU9FVzy4j+6FHguxkhH7SwROQUE46Vl4aYxMi46oE29dWdtLdK8KjUomx9nnHfoFgF5Mk6P/HUdEFPRP+81IFLv8wNArGo3j5crZGDN5PtCi+uROML9uoBBmhmrbnNHR2tuCUTTOyC4wYF3ng8cYJcGTKLYRsb/1LJHFo3o1QX52Krx1Al3gs5Eu4SoRa0erijgyIu3Mmb52aJLbPKkV/cIi2ZmCV59MZ3cip3qJjriUc4HdSTQAgGaJETZlnNZf/WCThHugRSjb2a2n2PprCRMhMRPvBMWfZcwtrWGROf9J/5lsEoPMabFoPFWFvlFEcWWoyhBv5513pL09LmvP6YdMnt6I5pD1Fm2KZnJxSXjfhr/flctiHHk8DS8Kg8oxDjAnnvWgbr3W6gZUk0z9rBA+m2DOGSQJPsPlNt9XgATRTu85IK1qxB8kXU2M1PHF3DZ+DdfamYP4SgvpSg/eEB8lohFly/zYs9rAawQ4oZNOYgLfn/dpriO7u4zjeUlyu5YcmeWEy9EuwYKNhx0z9Wa4QAB7vVRTauU0A8cKMo5fw+61ad35ogb2TcQo5Bv3iKbRmMY5k20DnH+zMRky 4CETBcFJ se+VxMCq6+QI8IU9N13XQifkO7H9T6874/MolGi7HMmZc+LjQFpgWLgE6MZqH1/bbpTN31qn61v9NTnVDmU0/FGsWOLTrqZgrpJE/11Vu5ihHbD0xDO1RQh/2+2LiiqkMw/+F6+RzJLXxjodhh4S4az7UmyFdkSsDpXXN7YBNDbKXI6PcHuTf0Sfw1+GqMWDrvK5ccEr81WVz1e6zSfSys4v7rDJ8vfIkb8Ltu+uU8XZM2mLUlRgw3JiFi06/L8Bk5GJalbSSSv4nX2rfBplcU/dH50j0ZHVItUnf0RbVmxsgTVyqFZG4q4Cd4Yx867V1jj5TdhQfWW/dCBuR4on9VuXy9zuzf7HmYgkLGpABrnlBCHqphC/URmiid6phfPWtItrC X-Bogosity: Ham, tests=bogofilter, spamicity=0.043845, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 31 Jan 2025, Lorenzo Stoakes wrote: >On Thu, Jan 16, 2025 at 05:30:58PM -0800, SeongJae Park wrote: >> Optimize redundant mmap lock operations from process_madvise() by >> directly doing the mmap locking first, and then the remaining works for >> all ranges in the loop. >> >> Signed-off-by: SeongJae Park > >I wonder if this might increase lock contention because now all of the >vector operations will hold the relevant mm lock without releasing after >each operation? That was exactly my concern. While afaict the numbers presented in v1 are quite nice, this is ultimately a micro-benchmark, where no other unrelated threads are impacted by these new hold times. >Probably it's ok given limited size of iov, but maybe in future we'd want >to set a limit on the ranges before we drop/reacquire lock? imo, this should best be done in the same patch/series. Maybe extend the benchmark to use IOV_MAX and find a sweet spot? Thanks, Davidlohr