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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 187EDC433F5 for ; Thu, 16 Dec 2021 02:26:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232915AbhLPC0Z (ORCPT ); Wed, 15 Dec 2021 21:26:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47144 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230021AbhLPC0X (ORCPT ); Wed, 15 Dec 2021 21:26:23 -0500 Received: from mail-yb1-xb36.google.com (mail-yb1-xb36.google.com [IPv6:2607:f8b0:4864:20::b36]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A6FBAC061574 for ; Wed, 15 Dec 2021 18:26:23 -0800 (PST) Received: by mail-yb1-xb36.google.com with SMTP id d10so60635754ybn.0 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=QfWFCuq3UiDSFvRhMY3pl7urPu2cEwuUgHAFWvtng+jDoITJR28iH5v/tLcjfk6LEr H2o5uEMiLdg2RAJI9praQmbLBATirZnc4N+XzYwL+fKKrCXoiUWETXZVkDRplB0w0URm 4slxaPnt0FCfy7zGYZWex2LsN3rive3Y+Ol73n+9R0zHs9UusvkG3/AqCIzJtX2/hwGy L7lE9GI/6It2UaPXUq6E6MMLzI0fkdSHDQ2xrHuaoEssUKbLX5xZL7qVGqVTkTiswWI9 dkqKOkc5wH5YvWaxvRN3tR4ZdO/UbpkyQ4F3/+zQDa9C2NctU+hJE6gStF1375JGFssy SPNw== X-Gm-Message-State: AOAM531ZdY2Y4q+0IX8fa2kYFFMt6ZwSLoBfFK5zmS/bEsN0/KVBWQ2E 9XYFvt1jmOPuKWQJCO9WqbdGsOspHqFtIoEfzaQSew== 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" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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