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 51FACC433EF for ; Thu, 16 Dec 2021 02:26:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AF5856B0071; Wed, 15 Dec 2021 21:26:34 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AA3F86B0073; Wed, 15 Dec 2021 21:26:34 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9451E6B0074; Wed, 15 Dec 2021 21:26:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0165.hostedemail.com [216.40.44.165]) by kanga.kvack.org (Postfix) with ESMTP id 817E26B0071 for ; Wed, 15 Dec 2021 21:26:34 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 45B298249980 for ; Thu, 16 Dec 2021 02:26:24 +0000 (UTC) X-FDA: 78922068288.14.9D8B814 Received: from mail-yb1-f170.google.com (mail-yb1-f170.google.com [209.85.219.170]) by imf04.hostedemail.com (Postfix) with ESMTP id A885040017 for ; Thu, 16 Dec 2021 02:26:23 +0000 (UTC) Received: by mail-yb1-f170.google.com with SMTP id g17so60388760ybe.13 for ; Wed, 15 Dec 2021 18:26:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=tB3x6NAjs5//RJkL9LMXnECDkkVJovad/BmtOHFhMgE=; b=fPk6aeZcvhGgQMP5Y03xNjGjJYJABGhLOrJVnFi9+ZvcXhIcWKvVkEfKBl7jDpc6di ff+uoIGdSTKZLedzJTuoM4I7SC7XEuuRhEs93ePqu2pkv8+q4cT1Gb5bsI3++G+P0HNN LUD5Jp+hEu6t8yoMZjv0zAKmhbudXDM3QQnnFliEej81XBXHZThAXL482gvmbmHuQKQ0 uhM0EUChCHju/cRcILqqDz0CHjvKxP2oPBn9AiIr2wf0gCdS4O6adX+dDtFiPoOw9J40 CrkwSvaJeGbdRaj+PsOd2AtHzCGd+5Pngc9N3CzZ6vn8dLJ7kjHH/+1sOAI5VLEodzzr dzHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=tB3x6NAjs5//RJkL9LMXnECDkkVJovad/BmtOHFhMgE=; b=OamoksXhFhxt4+NM+FVgb2oaNhSY4a6HEina7STL4TTiiPZ9sMzLEP0l8xuq4kCAuj Dua4W7Alut472GDQ8wphut3kTk2RMKB5WCzFeXjZqpM4J8rIHSTzWgsvolHO15MQTOpl U0vezxMmCZM/rcpxDAa9dwotNBzjbc8JPt8dLiP5vrrTveo5I/6dTJ+jYR9y2p8QJIMo 8vh/fK1F/hmHnPpvFeAQLWFciEuHyuoNOil4u0Rql4nyHg2ebby4WG/BdPxY0tRmlK5j kcSBBAKZOb1PfxzeB4Ri2ntM62iO2QI+h3hrvc+mSA1OvzYyIiuS0NQfj3cFQFPJntnA RjWg== X-Gm-Message-State: AOAM533SDsf7PHIvitJOCsikTNbJ93WXjQEat8jZ4VtZBA/Dncea0Ut8 r1gXdEmo8V/KoVtOOPqebJFeWjbElltbAp5+WQ0IXQ== X-Google-Smtp-Source: ABdhPJwxIGY4qVilnFG1zpsGyTqW5GuliNGeCUyhjN2AlwBqSAYaCnd/YG4ATFeHWCMVH3TuYpiGU0f+oiUNlNnoNpE= X-Received: by 2002:a5b:c0b:: with SMTP id f11mr10660172ybq.488.1639621582596; Wed, 15 Dec 2021 18:26:22 -0800 (PST) MIME-Version: 1.0 References: <20211208212211.2860249-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 15 Dec 2021 18:26:11 -0800 Message-ID: Subject: Re: [PATCH 4/3] mm: drop MMF_OOM_SKIP from exit_mmap To: Michal Hocko Cc: akpm@linux-foundation.org, rientjes@google.com, willy@infradead.org, hannes@cmpxchg.org, guro@fb.com, riel@surriel.com, minchan@kernel.org, kirill@shutemov.name, aarcange@redhat.com, christian@brauner.io, hch@infradead.org, oleg@redhat.com, david@redhat.com, jannh@google.com, shakeelb@google.com, luto@kernel.org, christian.brauner@ubuntu.com, fweimer@redhat.com, jengelh@inai.de, timmurray@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=fPk6aeZc; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf04.hostedemail.com: domain of surenb@google.com designates 209.85.219.170 as permitted sender) smtp.mailfrom=surenb@google.com X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: A885040017 X-Stat-Signature: 67q9bbaoi9t9yof79jwyz1yxqbaqkr3m X-HE-Tag: 1639621583-939977 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: On Thu, Dec 9, 2021 at 9:06 AM Suren Baghdasaryan wrote: > > On Thu, Dec 9, 2021 at 8:47 AM Michal Hocko wrote: > > > > On Thu 09-12-21 08:24:04, Suren Baghdasaryan wrote: > > > On Thu, Dec 9, 2021 at 1:12 AM Michal Hocko wrote: > > > > > > > > Do we want this on top? > > > > > > As we discussed in this thread > > > https://lore.kernel.org/all/YY4snVzZZZYhbigV@dhcp22.suse.cz, > > > __oom_reap_task_mm in exit_mmap allows oom-reaper/process_mrelease to > > > unmap pages in parallel with exit_mmap without blocking each other. > > > Removal of __oom_reap_task_mm from exit_mmap prevents this parallelism > > > and has a negative impact on performance. So the conclusion of that > > > thread I thought was to keep that part. My understanding is that we > > > also wanted to remove MMF_OOM_SKIP as a follow-up patch but > > > __oom_reap_task_mm would stay. > > > > OK, then we were talking past each other, I am afraid. I really wanted > > to get rid of this oom specific stuff from exit_mmap. It was there out > > of necessity. With a proper locking we can finally get rid of the crud. > > As I've said previously oom reaping has never been a hot path. > > > > If we really want to optimize this path then I would much rather see a > > generic solution which would allow to move the write lock down after > > unmap_vmas. That would require oom reaper to be able to handle mlocked > > memory. > > Ok, let's work on that and when that's done we can get rid of the oom > stuff in exit_mmap. I'll look into this over the weekend and will > likely be back with questions. As promised, I have a question: Any particular reason why munlock_vma_pages_range clears VM_LOCKED before unlocking pages and not after (see: https://elixir.bootlin.com/linux/latest/source/mm/mlock.c#L424)? Seems to me if VM_LOCKED was reset at the end (with proper ordering) then __oom_reap_task_mm would correctly skip VM_LOCKED vmas. https://lore.kernel.org/lkml/20180514064824.534798031@linuxfoundation.org/ has this explanation: "Since munlock_vma_pages_range() depends on clearing VM_LOCKED from vm_flags before actually doing the munlock to determine if any other vmas are locking the same memory, the check for VM_LOCKED in the oom reaper is racy." but "to determine if any other vmas are locking the same memory" explanation eludes me... Any insights? Thanks, Suren. > Thanks! > > > -- > > Michal Hocko > > SUSE Labs