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 X-Spam-Level: X-Spam-Status: No, score=-14.6 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8600CC433DF for ; Fri, 17 Jul 2020 15:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5CAC9204EA for ; Fri, 17 Jul 2020 15:17:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="S/eJBI5T" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726386AbgGQPR0 (ORCPT ); Fri, 17 Jul 2020 11:17:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbgGQPRX (ORCPT ); Fri, 17 Jul 2020 11:17:23 -0400 Received: from mail-lj1-x241.google.com (mail-lj1-x241.google.com [IPv6:2a00:1450:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 947A4C0619D3 for ; Fri, 17 Jul 2020 08:17:22 -0700 (PDT) Received: by mail-lj1-x241.google.com with SMTP id z24so13091916ljn.8 for ; Fri, 17 Jul 2020 08:17:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=CW/vI/yK0P533Yuk2TOJkvWJ7zd6tq/CXrAzQkJnwgU=; b=S/eJBI5TgyhFWJJh3yQWPlfplbzkZuAg1XzXAHFByNeqxg/CJ5L/ZzmjcuOrfTRUUd diZEWbViW1Y0y6E36f1HGrp1ho+e72mTaoY03zoTgs8RwGYTmkcKvsKFcIt3i8rwJmON VbwV5N21QVoSKSH0a43Qi2GT9TNZGQFBAVThlfi9UBMrDBCqrG+P9TCkKnAHqeAbT4JY eRByNOJMtJ+5KJhSJtnOEkARRIICKaS0SKZqTUhnCrci7x/CbmYuj2SqAfIWiNJwrMVs Bg1XBa0f+bdKGBbZlEaJpF6Byt/XgvP04M5a/5LoWGeUDFY4ECBonI8/ZEX+ug/E2cQF YoDQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=CW/vI/yK0P533Yuk2TOJkvWJ7zd6tq/CXrAzQkJnwgU=; b=mZC6P9WzSZvNWzWh5OQjMJgdPJzSPZVNdUianWy2dIqbF7h0iihKOer4gjmWBh4VDq gcSE547xlmILTvIzFWmkT5qZEfGL4/lrqS2q3SLnct2IwGRv6pnhPyRTV0t149/RUWr9 5rFkISXGM2LUlK8ZDp0zBfWD1nvvqneMfHA/Fxhshus5kCTA+xfy5XP3tultd+/HN00L QqjUlWWsrHawd6p4jcxMoB1QZqIjdHH3w0MuecCM38GlE5PGHl4PG/34fSCrGob7ZqHp J/IDwIegl084Y6dpZM7IyxBUoh7opvYFpLHtbL/qMNrgqmrkbc88CUmTOCQv3fh5+DFP rjfw== X-Gm-Message-State: AOAM532KG1cJo3hFke8bRfngu2uv4iMg7iU7ORiJgzicVHBw6KERoiC5 AeAhBMm+OXJaKEYLB798ony6aN/k+zdJigRvqxfC4w== X-Google-Smtp-Source: ABdhPJziey5oyrYePa+FU89+ldeQlFYPtdYe9O73g9psmVD/tqlhxa9TsiwuPeqqXUxiU5kaiC0zpHA28q+8vcapv5Q= X-Received: by 2002:a2e:978c:: with SMTP id y12mr4714541lji.270.1594999040547; Fri, 17 Jul 2020 08:17:20 -0700 (PDT) MIME-Version: 1.0 References: <20200717065313.8870-1-sjpark@amazon.com> In-Reply-To: <20200717065313.8870-1-sjpark@amazon.com> From: Shakeel Butt Date: Fri, 17 Jul 2020 08:17:09 -0700 Message-ID: Subject: Re: Re: [PATCH v18 06/14] mm/damon: Implement callbacks for the virtual memory address spaces To: SeongJae Park Cc: Andrew Morton , SeongJae Park , Jonathan.Cameron@huawei.com, Andrea Arcangeli , acme@kernel.org, alexander.shishkin@linux.intel.com, amit@kernel.org, benh@kernel.crashing.org, brendan.d.gregg@gmail.com, Brendan Higgins , Qian Cai , Colin Ian King , Jonathan Corbet , David Hildenbrand , dwmw@amazon.com, foersleo@amazon.de, Ian Rogers , jolsa@redhat.com, "Kirill A. Shutemov" , mark.rutland@arm.com, Mel Gorman , Minchan Kim , Ingo Molnar , namhyung@kernel.org, "Peter Zijlstra (Intel)" , Randy Dunlap , Rik van Riel , David Rientjes , Steven Rostedt , rppt@kernel.org, sblbir@amazon.com, shuah@kernel.org, sj38.park@gmail.com, snu@amazon.de, Vlastimil Babka , Vladimir Davydov , Yang Shi , Huang Ying , linux-damon@amazon.com, Linux MM , linux-doc@vger.kernel.org, LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, Jul 16, 2020 at 11:54 PM SeongJae Park wrote: > > On Thu, 16 Jul 2020 17:46:54 -0700 Shakeel Butt wrote: > > > On Mon, Jul 13, 2020 at 1:44 AM SeongJae Park wrote: > > > > > > From: SeongJae Park > > > > > > This commit introduces a reference implementation of the address space > > > specific low level primitives for the virtual address space, so that > > > users of DAMON can easily monitor the data accesses on virtual address > > > spaces of specific processes by simply configuring the implementation to > > > be used by DAMON. > > > > > > The low level primitives for the fundamental access monitoring are > > > defined in two parts: > > > 1. Identification of the monitoring target address range for the address > > > space. > > > 2. Access check of specific address range in the target space. > > > > > > The reference implementation for the virtual address space provided by > > > this commit is designed as below. > > > > > > PTE Accessed-bit Based Access Check > > > ----------------------------------- > > > > > > The implementation uses PTE Accessed-bit for basic access checks. That > > > is, it clears the bit for next sampling target page and checks whether > > > it set again after one sampling period. To avoid disturbing other > > > Accessed bit users such as the reclamation logic, the implementation > > > adjusts the ``PG_Idle`` and ``PG_Young`` appropriately, as same to the > > > 'Idle Page Tracking'. > > > > > > VMA-based Target Address Range Construction > > > ------------------------------------------- > > > > > > Only small parts in the super-huge virtual address space of the > > > processes are mapped to physical memory and accessed. Thus, tracking > > > the unmapped address regions is just wasteful. However, because DAMON > > > can deal with some level of noise using the adaptive regions adjustment > > > mechanism, tracking every mapping is not strictly required but could > > > even incur a high overhead in some cases. That said, too huge unmapped > > > areas inside the monitoring target should be removed to not take the > > > time for the adaptive mechanism. > > > > > > For the reason, this implementation converts the complex mappings to > > > three distinct regions that cover every mapped area of the address > > > space. Also, the two gaps between the three regions are the two biggest > > > unmapped areas in the given address space. The two biggest unmapped > > > areas would be the gap between the heap and the uppermost mmap()-ed > > > region, and the gap between the lowermost mmap()-ed region and the stack > > > in most of the cases. Because these gaps are exceptionally huge in > > > usual address spacees, excluding these will be sufficient to make a > > > reasonable trade-off. Below shows this in detail:: > > > > > > > > > > > > > > > (small mmap()-ed regions and munmap()-ed regions) > > > > > > > > > > > > > > > Signed-off-by: SeongJae Park > > > Reviewed-by: Leonard Foerster > > [snip] > > > + > > > +static void damon_mkold(struct mm_struct *mm, unsigned long addr) > > > +{ > > > + pte_t *pte = NULL; > > > + pmd_t *pmd = NULL; > > > + spinlock_t *ptl; > > > + > > > + if (follow_pte_pmd(mm, addr, NULL, &pte, &pmd, &ptl)) > > > + return; > > > + > > > + if (pte) { > > > + if (pte_young(*pte)) { > > > > Any reason for skipping mmu_notifier_clear_young()? Why exclude VMs as > > DAMON's target applications? > > Obviously my mistake, thank you for pointing this! I will add the function > call in the next spin. > Similarly mmu_notifier_test_young() for the damon_young(). BTW I think we can combine ctx->prepare_access_checks() and ctx->check_accesses() into one i.e. get the young state for the previous cycle and mkold for the next cycle in a single step. I am wondering if there is any advantage to having "Page Idle Tracking" beside DAMON. I think we can make them mutually exclusive. Once we have established that I think DAMON can steal the two page flag bits from it and can make use of them. What do you think?