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 D9E54C4332F for ; Tue, 22 Nov 2022 16:27:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 35E968E0001; Tue, 22 Nov 2022 11:27:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 30E816B0073; Tue, 22 Nov 2022 11:27:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1D72A8E0001; Tue, 22 Nov 2022 11:27:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 0F5066B0071 for ; Tue, 22 Nov 2022 11:27:52 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id AFF05A0B32 for ; Tue, 22 Nov 2022 16:27:51 +0000 (UTC) X-FDA: 80161609542.22.D9634B0 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) by imf22.hostedemail.com (Postfix) with ESMTP id 5B81BC000C for ; Tue, 22 Nov 2022 16:27:51 +0000 (UTC) Received: by mail-pj1-f73.google.com with SMTP id k9-20020a17090a39c900b0021671e97a25so7830050pjf.1 for ; Tue, 22 Nov 2022 08:27:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=8PDPHpg3FoSEfatXEdymj1J6bzmmuafnhuxNaKgp3vY=; b=VMOr0enba7bo5QpD9v2s1jCYse9HichRnVIZL9vq8t91LyPi5jzYYCzu0vRmmpXFhP mVWH49GSnRF8Ptu1PT2SxT0AI/gDz4VEkyN57D70TI4dQ9lmmfkDSiUVlGBB7/9Q1IdE 5A6bcubRqRqLZ9cMiUBw9UwmRwoxMIAJ89Ye45p7rmDQeLAtrZUaTuGRhebLZw4WVV7J oA1WHHSn5BKWoj9IiGxJUrvRXaX8TcfpFI5YIdJ0d882ACc4ztGqyPTecVtYWp5fEawd mv+BsqJ4auMv9ZXz023CHvmV4NvmHsJn0jskYIHpZ3YniBHX2+Ve49CjhFe/NwPW8yk5 pIWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=8PDPHpg3FoSEfatXEdymj1J6bzmmuafnhuxNaKgp3vY=; b=0ECjI7fwPo6OiZhmlIbWhvQY0yoaGbx2fsSK0W9jpakWg9QCxERvRDIV021ARMlRYY 6It3NsLbYkrgQLcrdu6PKmDNu8Fj5P76wmexc0j6ynAePHSrwPalPUpnuVj+658x6ZA+ yaezWh6U+XRR7LxMFCKZqHxe+o4FSps2KvxBGKXFmRHN7K/kg+SoPQ26belWVGUSPgLZ n0qr+XazDfriehYV8djtLTEJ/hMEIgdSs8kNW5+WlZwzW7yP3V74lOlE2pp0wNewrCx8 EsSXsqGguDBAHQ6BJUawjApIq062oA/a4r7PKwx53Lmd1Ry3jhcWi8FZfWH4HzamvweB MZqg== X-Gm-Message-State: ANoB5ployX+cNO9MQZe/EFCecXw24NPVhaAdBcZe9jMscfvdpKRji4F6 OYbWWgYth5ncxeEqlh4Ujovvm9WXuviHMA== X-Google-Smtp-Source: AA0mqf5RNc74C8zoBBjjWCIqYQecB9p2pLvXj69GJPKNSS3Soq6P4eXgBypP82aZlW1QnJdjVq0+pnjMCpsrRQ== X-Received: from shakeelb.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:262e]) (user=shakeelb job=sendgmr) by 2002:a17:90a:d106:b0:213:1944:dde2 with SMTP id l6-20020a17090ad10600b002131944dde2mr26049964pju.193.1669134470008; Tue, 22 Nov 2022 08:27:50 -0800 (PST) Date: Tue, 22 Nov 2022 16:27:47 +0000 In-Reply-To: Mime-Version: 1.0 References: <5f52de70-975-e94f-f141-543765736181@google.com> <20221121165938.oid3pemsfkaeq3ws@google.com> Message-ID: <20221122162747.opnte2csfr5hors2@google.com> Subject: Re: [PATCH 0/3] mm,thp,rmap: rework the use of subpages_mapcount From: Shakeel Butt To: Linus Torvalds Cc: Hugh Dickins , Andrew Morton , Johannes Weiner , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Vlastimil Babka , Peter Xu , Yang Shi , John Hubbard , Mike Kravetz , Sidhartha Kumar , Muchun Song , Miaohe Lin , Naoya Horiguchi , Mina Almasry , James Houghton , "Zach O'Keefe" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669134471; a=rsa-sha256; cv=none; b=vMnnORt4rKlTB5eUpQbwK8ZQQfuwA19ghIcOuWxJPNrfQX1VZt6Peqx/6/Gsmuyv6uNnME CUhqrRWyZ0xORyht5+8womfx84zleNX035oE32oL6mNT2tfPPI2IFBHrl60mLvWKnMavzH 8mzc+0NmKUXZM+I+E12B3msCNN64C9U= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=VMOr0enb; spf=pass (imf22.hostedemail.com: domain of 3hvh8YwgKCI09yr1vv2sx55x2v.t532z4BE-331Crt1.58x@flex--shakeelb.bounces.google.com designates 209.85.216.73 as permitted sender) smtp.mailfrom=3hvh8YwgKCI09yr1vv2sx55x2v.t532z4BE-331Crt1.58x@flex--shakeelb.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669134471; 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=8PDPHpg3FoSEfatXEdymj1J6bzmmuafnhuxNaKgp3vY=; b=kuLm9O4AxuwNDXZa8hx757ce2Q/BfZKhBQTfr3+GAC3q8z1Nd39+jXt9WRx0FtP6fzldKL 1rzJXJTZqTtA3uRWC404iKohmVVzJzNtiuQdICot/+D1Zfs/3z1oPIhrgqQHsUB7dSVPbU Fj7X6Km8Kun7+ObENoWAr3gpkVmwdio= X-Rspam-User: X-Rspamd-Queue-Id: 5B81BC000C Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=VMOr0enb; spf=pass (imf22.hostedemail.com: domain of 3hvh8YwgKCI09yr1vv2sx55x2v.t532z4BE-331Crt1.58x@flex--shakeelb.bounces.google.com designates 209.85.216.73 as permitted sender) smtp.mailfrom=3hvh8YwgKCI09yr1vv2sx55x2v.t532z4BE-331Crt1.58x@flex--shakeelb.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: 9fafoicjeb4coy47ad7zc5tru3xaaqq4 X-Rspamd-Server: rspam10 X-HE-Tag: 1669134471-7596 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 Mon, Nov 21, 2022 at 09:16:58AM -0800, Linus Torvalds wrote: > On Mon, Nov 21, 2022 at 8:59 AM Shakeel Butt wrote: > > > > Is there a plan to remove lock_page_memcg() altogether which I missed? = I > > am planning to make lock_page_memcg() a nop for cgroup-v2 (as it shows > > up in the perf profile on exit path) >=20 > Yay. It seems I'm not the only one hating it. >=20 > > but if we are removing it then I should just wait. >=20 > Well, I think Johannes was saying that at least the case I disliked > (the rmap removal from the page table tear-down - I strongly suspect > it's the one you're seeing on your perf profile too) Yes indeed that is the one. - 99.89% 0.00% fork-large-mmap [kernel.kallsyms] [k] entry_SYSCALL= _64_after_hw=E2=97=86 entry_SYSCALL_64_after_hwframe =20 - do_syscall_64 =20 - 48.94% __x64_sys_exit_group =20 do_group_exit =20 - do_exit =20 - 48.94% exit_mm =20 mmput =20 - __mmput =20 - exit_mmap =20 - 48.61% unmap_vmas =20 - 48.61% unmap_single_vma =20 - unmap_page_range =20 - 48.60% zap_p4d_range =20 - 44.66% zap_pte_range =20 + 12.61% tlb_flush_mmu =20 - 9.38% page_remove_rmap =20 2.50% lock_page_memcg =20 2.37% unlock_page_memcg =20 0.61% PageHuge =20 4.80% vm_normal_page =20 2.56% __tlb_remove_page_size 0.85% lock_page_memcg =20 0.53% PageHuge =20 2.22% __tlb_remove_page_size =20 0.93% vm_normal_page =20 0.72% page_remove_rmap > can be removed > entirely as long as it's done under the page table lock (which my > final version of the rmap delaying still was). >=20 > See >=20 > https://lore.kernel.org/all/Y2llcRiDLHc2kg%2FN@cmpxchg.org/ >=20 > for his preliminary patch. >=20 > That said, if you have some patch to make it a no-op for _other_ > reasons, and could be done away with _entirely_ (not just for rmap), > then that would be even better. I am actually looking at deprecating the whole "move charge" funcitonality of cgroup-v1 i.e. the underlying reason lock_page_memcg exists. That already does not work for couple of cases like partially mapped THP and madv_free'd pages. Though that deprecation process would take some time. In the meantime I was looking at if we can make these functions nop for cgroup-v2. thanks, Shakeel