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 7EE34D462C6 for ; Wed, 13 Nov 2024 15:47:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 080BF6B00F8; Wed, 13 Nov 2024 10:47:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 009676B00F9; Wed, 13 Nov 2024 10:47:55 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DEC5D6B00FC; Wed, 13 Nov 2024 10:47:55 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id B27E06B00F8 for ; Wed, 13 Nov 2024 10:47:55 -0500 (EST) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 70825120AF1 for ; Wed, 13 Nov 2024 15:47:55 +0000 (UTC) X-FDA: 82781500326.03.71725C2 Received: from mail-qt1-f171.google.com (mail-qt1-f171.google.com [209.85.160.171]) by imf08.hostedemail.com (Postfix) with ESMTP id 014BF160024 for ; Wed, 13 Nov 2024 15:47:24 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=zg37X8Ru; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf08.hostedemail.com: domain of surenb@google.com designates 209.85.160.171 as permitted sender) smtp.mailfrom=surenb@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1731512810; a=rsa-sha256; cv=none; b=sB5JL69agiysEdF8GJbnzqsVoXPgZqUkji166y0aoGIQ+fMZ9dsR0zTcC9CU42fMTcfF9E e9jvdabpiLhKi0cHbNlj1SwzNlPpkJL45cTWh63dyOJbYMC9ErAaOe0HrSqKxAeyOf3qmc E4+jAd7Xq8h8YQ4dfFuYajgmxjm2MHU= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=zg37X8Ru; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf08.hostedemail.com: domain of surenb@google.com designates 209.85.160.171 as permitted sender) smtp.mailfrom=surenb@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1731512810; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to: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=PIGBOTsMnscnNMh+xLfadwOTEgGK5dsWKgIHabjBrcw=; b=ZUFYzy6oR1sHFvrwDC++Y+FiT7rp7vL3qHzskGZEX96eW/eLLxsgsFZyuKBkm20QCjlFKp uNQUmKyNUOxBWA/UYQh3GHYCbQNMXunMiEL+wpMCUwLde1HBqTL1C3sJlL/W2KFZuI+nfu onue8BTSjtYwRV3v4MF6QNY1TqoNStI= Received: by mail-qt1-f171.google.com with SMTP id d75a77b69052e-460a8d1a9b7so261821cf.1 for ; Wed, 13 Nov 2024 07:47:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1731512873; x=1732117673; darn=kvack.org; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=PIGBOTsMnscnNMh+xLfadwOTEgGK5dsWKgIHabjBrcw=; b=zg37X8RuaGTW/koL6mhK9YUzq6UqdPnXbi5Rum9b/Rjw+HXR97AEuZdR8NVfffePWQ hpWr5zLHhyq9+oB05nc8TNPHlDSrEcOo+AmsbHq8ttbKcXqpOVkHqt711yQhiKrLOl2a FCy0dMUt3WMQ/oapIpGFdQhDv6t/WPJ9dbVZo6FMSKvCteHSAUhDV2TB5CmBQ6zMc4BY Gtx4i3ApVP3F9grajhFkIxbjzRMPAv+sA/NnMskqyJ3t6+KMnY1nBUe5++iUvBt2pL1i QvjOuvONSrM3XmyHCR19hUzSsdfZEpq3JfgAW9QgRt/OQVFh2QNDanDzqgqCrWfiUpv0 h2pg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1731512873; x=1732117673; h=content-transfer-encoding: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=PIGBOTsMnscnNMh+xLfadwOTEgGK5dsWKgIHabjBrcw=; b=Uld7QUHFAuYxAiIzJe5zrZKKOQ9nkUyYTsubC1y9ZIukKmEbopvj7YvrvmEpGYlW1V 8UnW7e6nJyR/MMB9xLx/8hTgUcCjd7u1vlUfV/G2dJkFtcQZJfUwkRodaNqEmLEAtB+C RZ1SCKv0h5Qpmxa0WvNkl4izxNc10tgMoqODkcFCcqmy78QGjA8dMydBqFvu6QMtliXx DPFN0/w79wGMMdYKalEuxDr/ny9BY5vkCCqk92fV8ZgNCc1qvXmynYH2g+1Kk5gpUXbW uVI933jRWx8GppTI7msUfG3wVwOikSLvfIg0Z0UE+9XE6AzEzzRVIo2PFcJNcSc1pan2 uFbw== X-Forwarded-Encrypted: i=1; AJvYcCUXeYAeCFouNK6X7Sng5oRebZ6ZLXn4EE13YMpdLHWg5ZQqhHztjFqeLbqKYTG7vpLM3KSKBWR4+Q==@kvack.org X-Gm-Message-State: AOJu0Yx4J9P6+iY/L85yVXvhBhhPXNHifyCCw+YNESBQ3C6qnXtTQYQ3 7MSzuK/J5ZSOThOZ4rARz2eR7pKblI3sdzoMmr8c0qerGZh1OII98OIH5hcNpaq+sVeZi699NTh o0uaJp98htr4QNPbsMIyahoATNvrn8rOl7va5 X-Gm-Gg: ASbGncsGnpO5GBkIk5/8VUCwj6PM/ojb8fn3jwvEfoZGZ9FB8W2QUCx7ZFuQVj0eyzt VNcjjpfhqtVEDqdmrNrgFinD8QmzJXTA= X-Google-Smtp-Source: AGHT+IHsSjvVs37dTOPQ3ErUpR9I/gQJNeIrUh7ZMqQExz8MALQ2x9yDJvhWkgfyU4Kq0PkEtMwp2O/D/tQ8ohR1+N8= X-Received: by 2002:ac8:5915:0:b0:462:ffaa:938d with SMTP id d75a77b69052e-4634bbeba0emr3417911cf.10.1731512872451; Wed, 13 Nov 2024 07:47:52 -0800 (PST) MIME-Version: 1.0 References: <20241112194635.444146-1-surenb@google.com> <20241112194635.444146-5-surenb@google.com> <54b8d0b9-a1c7-4c1b-a588-2e5308a977fb@suse.cz> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 13 Nov 2024 07:47:41 -0800 Message-ID: Subject: Re: [PATCH v2 4/5] mm: make vma cache SLAB_TYPESAFE_BY_RCU To: "Liam R. Howlett" , Suren Baghdasaryan , Matthew Wilcox , Vlastimil Babka , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 014BF160024 X-Rspamd-Server: rspam01 X-Stat-Signature: oprj7hbthf9bn1wdbrqb8ystry1ut46g X-HE-Tag: 1731512844-184786 X-HE-Meta: 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 Z8HM7l9X GvGXr2yCzj6fUdGKpK5XlDaOq17Yqls/Z1CfkDuRmU+33RsBAzCCrYV6Ab8cMXzP12jEZAkY6HWfwXZMj7LZGSuSoX9/Idf1TUnO0XjkZKKhzH9lPptnDjZ3lmMTq1Yb7SBzFJaozztF1GTwqfdXTWKbjVg6WbS8jeRhRdcEljkvLxmbjaklkxvyEG+AOdnyvFVu9NGWDN16pmcqvEAHAtJHciYqNGo9oj1kz3qIkS1nKOU/BvsAnUWs/nvgUBav5tdyQ5NwKogcZNDxi7gSkwT7H2WjtKLTS64QzxH+1QnvXqt+vFvDGv9QG209S+jOApTf/p+enmoQ6E6duWAedzf+kLG/8z/ER3Z7EHYX0T4GfgZvR8etx9/mJSw== 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 Wed, Nov 13, 2024 at 7:29=E2=80=AFAM Liam R. Howlett wrote: > > * Suren Baghdasaryan [241113 10:25]: > > On Wed, Nov 13, 2024 at 7:23=E2=80=AFAM 'Liam R. Howlett' via kernel-te= am > > wrote: > > > > > > * Matthew Wilcox [241113 08:57]: > > > > On Wed, Nov 13, 2024 at 07:38:02AM -0500, Liam R. Howlett wrote: > > > > > > Hi, I was wondering if we actually need the detached flag. Coul= dn't > > > > > > "detached" simply mean vma->vm_mm =3D=3D NULL and we save 4 byt= es? Do we ever > > > > > > need a vma that's detached but still has a mm pointer? I'd hope= the places > > > > > > that set detached to false have the mm pointer around so it's n= ot inconvenient. > > > > > > > > > > I think the gate vmas ruin this plan. > > > > > > > > But the gate VMAs aren't to be found in the VMA tree. Used to be t= hat > > > > was because the VMA tree was the injective RB tree and so VMAs coul= d > > > > only be in one tree at a time. We could change that now! > > > > > > \o/ > > > > > > > > > > > Anyway, we could use (void *)1 instead of NULL to indicate a "detac= hed" > > > > VMA if we need to distinguish between a detached VMA and a gate VMA= . > > > > > > I was thinking a pointer to itself vma->vm_mm =3D vma, then a check f= or > > > this, instead of null like we do today. > > > > The motivation for having a separate detached flag was that vma->vm_mm > > is used when read/write locking the vma, so it has to stay valid even > > when vma gets detached. Maybe we can be more cautious in > > vma_start_read()/vma_start_write() about it but I don't recall if > > those were the only places that was an issue. > > We have the mm form the callers though, so it could be passed in? Let me try and see if something else blows up. When I was implementing per-vma locks I thought about using vma->vm_mm to indicate detached state but there were some issues that caused me reconsider. > > > > > > > > > Either way, we should make it a function so it's easier to reuse for > > > whatever we need in the future, wdyt? > > > > > > To unsubscribe from this group and stop receiving emails from it, sen= d an email to kernel-team+unsubscribe@android.com. > > >