From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6931BD41D41 for ; Tue, 12 Nov 2024 00:11:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E6DB58D0013; Mon, 11 Nov 2024 19:11:06 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E1CD78D0001; Mon, 11 Nov 2024 19:11:06 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C96778D0013; Mon, 11 Nov 2024 19:11:06 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id A43AC8D0001 for ; Mon, 11 Nov 2024 19:11:06 -0500 (EST) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 607D21A0902 for ; Tue, 12 Nov 2024 00:11:06 +0000 (UTC) X-FDA: 82775512092.18.EBD00A0 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf30.hostedemail.com (Postfix) with ESMTP id 389898001D for ; Tue, 12 Nov 2024 00:09:47 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=nqNOw4zU; dmarc=none; spf=pass (imf30.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1731370202; a=rsa-sha256; cv=none; b=bCpWWYzh+Aq6AraIKFt8/2AkqiiwZqLRUvf1NViYiwf1djgbA9hvS++QuYAsZ3DakdRQQj oELLiKunxK2WlUtheHMoEj7CaYoJ4kmVtxBVwb2/+6kgfCqvWgq19+xdnu//XAE4kI8yJ8 NJ0ilz0yJvl0HTgqmP5g65AsxM/0R/A= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=nqNOw4zU; dmarc=none; spf=pass (imf30.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1731370202; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Gb6u92lpbXLXXGAT3H+Qo5ZnjZXt+FNSoePUD61TycM=; b=aXBFYhuYNuMEkovaXGNZOw2Y4jK4PCiZFJlW1QZ+9sBs+HWN7Ek0BA84g6ghV8QR5n+pWm cv4C/mF04/XAgUbqwVQLdZnnzsno7Mw/zoforuPtGbUvUKlls3SWT+MbSkZV8/j7Oad4/D lACPcCTnA0zxrk8N/OHAzL3P8vnXDdk= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 6BD955C5DD5; Tue, 12 Nov 2024 00:10:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B32F6C4CECF; Tue, 12 Nov 2024 00:11:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1731370263; bh=3DPDYTaWToG+1nItkCo1KdEPJK4TtL89ZByaok+uIxs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=nqNOw4zUVCIXgOu+pl5rQuZpt5FpkJg1atcHOguLCPqCWNgfv1DtA95TZc7B8JRA2 wAbA5LfUKnAYibKZYb+Wm3clv3LUY5/mRo1mBgKwhYiWZwFEhR/gL7FQ4q+mgsKG5I CpmTIrMXyW9FWUGlMPvS5Wm/QyaFGpyXitT1qphY= Date: Mon, 11 Nov 2024 16:11:02 -0800 From: Andrew Morton To: Suren Baghdasaryan Cc: willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 0/4] move per-vma lock into vm_area_struct Message-Id: <20241111161102.e047bce4adfbf38002b7a9cf@linux-foundation.org> In-Reply-To: References: <20241111205506.3404479-1-surenb@google.com> <20241111221839.w4rqqlvvkm42jdgm@offworld> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 389898001D X-Rspamd-Server: rspam01 X-Stat-Signature: xmcf46y4zha8bd9ic6etu883ek4zwxxu X-HE-Tag: 1731370187-923876 X-HE-Meta: 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 j9HMkc1Q 1EphooXNfLqV2KpbzyC0+felOihXwATi6vEQdt5SkaPLYn58/ts9FarHkx/H05zmJBT2LlzqX5yOmvCKeePoJH0GApHKUWMK5SLyb94nr0DSDYOscBLy4pDo3CEZ4SahcWR06jVlFNEjHBs+j4+LzrKSPkayNSMMOOb/jxO9v21w28nTgYfohmCJJKyrMWSOUbJFZ/Ih4zPq8BaO7EHoLKCZy5xjDrwXVULeufhHV6SjlFfDHjmXsZmE06hw6ppiSLNnnRVlZ5b1gd1fY6GvQ1VXjmhpqiNyEQwOppKkiRQkRC1FA2v83UXUhwq3lBvaj6SioN8MDaEdHBGCAPGz27CPzmxxEuMB+wHdSkxj7HYFcp57PYSfzz96He24DAzu+4IMoNEEzGJLP4b35K9utddMizw== 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: List-Subscribe: List-Unsubscribe: On Mon, 11 Nov 2024 15:19:22 -0800 Suren Baghdasaryan wrote: > On Mon, Nov 11, 2024 at 2:18 PM Davidlohr Bueso wrote: > > > > On Mon, 11 Nov 2024, Suren Baghdasaryan wrote: > > > > >To minimize memory overhead, vm_lock implementation is changed from > > >using rw_semaphore (40 bytes) to an atomic (8 bytes) and several > > >vm_area_struct members are moved into the last cacheline, resulting > > >in a less fragmented structure: > > > > I am not a fan of building a custom lock, replacing a standard one. > > Understandable. If we're going to invent a new lock type, I'm thinking we should do that - make it a standaline thing, add full lockdep support, etc. I wonder if we could remove the lock from the vma altogeher and use an old-fashioned hashed lock. An array of locks indexed by the vma address. It might work well enough, although sizing the array would be difficult.