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 259F1C43334 for ; Thu, 16 Jun 2022 21:56:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 956F76B0071; Thu, 16 Jun 2022 17:56:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8DF486B0072; Thu, 16 Jun 2022 17:56:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 758656B0073; Thu, 16 Jun 2022 17:56:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 5FFEF6B0071 for ; Thu, 16 Jun 2022 17:56:32 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 353A934F0E for ; Thu, 16 Jun 2022 21:56:32 +0000 (UTC) X-FDA: 79585458624.02.92ACB53 Received: from mail-vs1-f49.google.com (mail-vs1-f49.google.com [209.85.217.49]) by imf30.hostedemail.com (Postfix) with ESMTP id BA66780099 for ; Thu, 16 Jun 2022 21:56:31 +0000 (UTC) Received: by mail-vs1-f49.google.com with SMTP id x9so2423577vsg.13 for ; Thu, 16 Jun 2022 14:56:31 -0700 (PDT) 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=IjlM3vbou88b5LgLylvLtPzb4A4wi5OpV/vwF2bF6vA=; b=luZH+ZNaG5KVeSHWoVUQPxhwIvaNc10bfWOshMf4MSOUNEufKJmDGhFIsXYipizIrL kvXIo35UZLhZs5NAkxN02wDob9it6O3RpNIBEOFNATLHtrk60YwH8SkXqa4KZ63SZ5ln 3K6ssQHFLWhAl3AJAkTUAQAjzmuJ3RklEZENWSps45I/F4m0teJKOHYzQd8QoFGTimjD /jA+DmwfWTmO/GKPI5aqKlAYB7BHTD+OJemVEqCa6mhcELgpgWwvzzuG1LHv9MREzpUG rhEP0ul00polFwwQtXryB9iGzIQSUBiHVlMBZz3EyCORkNC0mc8S874U5Rl21v/w7oUI VeaQ== 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=IjlM3vbou88b5LgLylvLtPzb4A4wi5OpV/vwF2bF6vA=; b=Nn7fyr6iYKrncqt/l/8JtkTSzCKKwYfiDRNdkBU+hJvgJ3ypNeiHuU2P+dq7jNgTR8 XHGkiUzgSWKosUb+yTL/G3uFpRLHm9OgGmahmnXhwJfeqTHIh6Y5yb2MIpPlMGrjnHHJ P3RaTmMs9MtXsPr3qwvTwd2QbzxO7NwlTIlW7xrJ/rBoK2KrZjVArxkYWIiRkWb9iNOl xhBjXhCqfSQ1/rvhJVzaPcv9XcLpZtgSEWEjso3Ksqr1Fdd8VF7jePCn57mm3euPPQSd /L9OhrKXtxt5K5lzvRjOR2zUqXjZ+tfytxYBFSHJKj8fnspOuhY7ItTQ2MVOdbdaqI/7 aZ1A== X-Gm-Message-State: AJIora9QLB0o2f39BkD3THpiwWfu6rIhD0bm1xW3wN49yvJ70BaZtjcn Io0s9asVizVYb8wpisP2sbpoXsiobypUytysbyDo0A== X-Google-Smtp-Source: AGRyM1tlXhUmHC3noZOjt2OwAeuKugI4s20YGAvEyporuM+MgUc1WLNWUacFUVElKg67zIxZuSJVRLmo22Y+UbnVJ+0= X-Received: by 2002:a67:b907:0:b0:34b:d597:d6e8 with SMTP id q7-20020a67b907000000b0034bd597d6e8mr3230751vsn.84.1655416590903; Thu, 16 Jun 2022 14:56:30 -0700 (PDT) MIME-Version: 1.0 References: <20220518014632.922072-1-yuzhao@google.com> <20220518014632.922072-8-yuzhao@google.com> <20220607102135.GA32448@willie-the-truck> <20220607104358.GA32583@willie-the-truck> In-Reply-To: From: Yu Zhao Date: Thu, 16 Jun 2022 15:55:54 -0600 Message-ID: Subject: Re: [PATCH v11 07/14] mm: multi-gen LRU: exploit locality in rmap To: Barry Song <21cnbao@gmail.com> Cc: Linus Torvalds , Will Deacon , Andrew Morton , Linux-MM , Andi Kleen , Aneesh Kumar , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Peter Zijlstra , Tejun Heo , Vlastimil Babka , LAK , Linux Doc Mailing List , LKML , x86 , Kernel Page Reclaim v2 , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain , huzhanyuan@oppo.com Content-Type: text/plain; charset="UTF-8" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655416591; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IjlM3vbou88b5LgLylvLtPzb4A4wi5OpV/vwF2bF6vA=; b=ziVVDYtOhi7GjFsF3LMjlcAKGB3k275LmILmKPEfMcqwa+Ptsyl1X2VZJ0OApzLjiPLT/3 Buho0zocZyTeUYt7eF7XfMab0CTFZrL85A0qjL1KQgDfkr1xo5Q9cFMOhiC5mogRkfbcdG MYo8VijQs/DvQiUGcnajDOJf2eM4wvY= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655416591; a=rsa-sha256; cv=none; b=5PsYgY6kwfDT60NDPRQs6DjRNsmltdFHZkghmvVmmEudbt4BPfj3IrIr6MUTfGVPUtx/C4 XhKePBGBUiqJzGt7TYHsnQJwnHkxTBJJjkTCtDF1ijmWtpgUwY/fXpgIV9kuI6JJZJ0sY1 XQPFCw0n1eldCsgXuGg4RszFgJi2PrM= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=luZH+ZNa; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf30.hostedemail.com: domain of yuzhao@google.com designates 209.85.217.49 as permitted sender) smtp.mailfrom=yuzhao@google.com X-Stat-Signature: a6mtsn8u18jkr1cqyd85wrao1ibdf8up X-Rspamd-Queue-Id: BA66780099 Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=luZH+ZNa; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf30.hostedemail.com: domain of yuzhao@google.com designates 209.85.217.49 as permitted sender) smtp.mailfrom=yuzhao@google.com X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1655416591-222698 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 Wed, Jun 8, 2022 at 4:46 PM Barry Song <21cnbao@gmail.com> wrote: > > On Thu, Jun 9, 2022 at 3:52 AM Linus Torvalds > wrote: > > > > On Tue, Jun 7, 2022 at 5:43 PM Barry Song <21cnbao@gmail.com> wrote: > > > > > > Given we used to have a flush for clear pte young in LRU, right now we are > > > moving to nop in almost all cases for the flush unless the address becomes > > > young exactly after look_around and before ptep_clear_flush_young_notify. > > > It means we are actually dropping flush. So the question is, were we > > > overcautious? we actually don't need the flush at all even without mglru? > > > > We stopped flushing the TLB on A bit clears on x86 back in 2014. > > > > See commit b13b1d2d8692 ("x86/mm: In the PTE swapout page reclaim case > > clear the accessed bit instead of flushing the TLB"). > > This is true for x86, RISC-V, powerpc and S390. but it is not true for > most platforms. > > There was an attempt to do the same thing in arm64: > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1793830.html > but arm64 still sent a nosync tlbi and depent on a deferred to dsb : > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1794484.html Barry, you've already answered your own question. Without commit 07509e10dcc7 arm64: pgtable: Fix pte_accessible(): #define pte_accessible(mm, pte) \ - (mm_tlb_flush_pending(mm) ? pte_present(pte) : pte_valid_young(pte)) + (mm_tlb_flush_pending(mm) ? pte_present(pte) : pte_valid(pte)) You missed all TLB flushes for PTEs that have gone through ptep_test_and_clear_young() on the reclaim path. But most of the time, you got away with it, only occasional app crashes: https://lore.kernel.org/r/CAGsJ_4w6JjuG4rn2P=d974wBOUtXUUnaZKnx+-G6a8_mSROa+Q@mail.gmail.com/ Why?