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 78879C433EF for ; Thu, 10 Mar 2022 00:01:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 124C88D0003; Wed, 9 Mar 2022 19:01:10 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0AE328D0001; Wed, 9 Mar 2022 19:01:10 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E69B28D0003; Wed, 9 Mar 2022 19:01:09 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id D6F418D0001 for ; Wed, 9 Mar 2022 19:01:09 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id A436E80DCA for ; Thu, 10 Mar 2022 00:01:09 +0000 (UTC) X-FDA: 79226521458.13.ABB1BDA Received: from mail-lf1-f43.google.com (mail-lf1-f43.google.com [209.85.167.43]) by imf16.hostedemail.com (Postfix) with ESMTP id 18DCC180011 for ; Thu, 10 Mar 2022 00:01:08 +0000 (UTC) Received: by mail-lf1-f43.google.com with SMTP id n19so6556811lfh.8 for ; Wed, 09 Mar 2022 16:01:08 -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=WQgS6lOyLDfVKHIwvM6TO9ZwbK1iC5yKsSbkiuG5xBM=; b=jiHj2JDxJRQmzYXaWy/nzeXUB/HS/W65P2pSShQ90pqyLjRXZJVT7zwk7BjcDgxnS2 r3JcXzWo9jMuorTc+cDtYJ4fEJ7ofYnceG02gyAhQNdCpCr4XURo/NdrBzOiqDKcGVYx Lfr/GvYhM1HitygP1cLRkhyyNrrF0Es5cp8R2gU1tHBXuod0TMjj4LzpHC/l6heFFS0D gh562CmndHhc6uh8OsJCiwjULuZo2YvttmczMOmw+UZppeKMaSLzP1RALcTOZLGGtQ1B 8e/l51Ln0Yg3z/w/EJA1QA2bt4DxJWpNjPvgb6q/RaM/SKTt21+LcOmQrXUbRrAON8eN O99Q== 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=WQgS6lOyLDfVKHIwvM6TO9ZwbK1iC5yKsSbkiuG5xBM=; b=iiksQmFmuExD+nsA4JWxQUgvR4ggXdcvglUbJBTHOrzTOrW5UuqywKxfKS7VC8sW7v wxerPT4zZjbQQHK2tqPcchDd4V6RNe4vOG51eoQBQTPJWIG/mBFBH42+NZM/Z0PlaoZI NTJ/Tz9rRnrfmS8lm/PNB+SlYQ786Lf2bSo8pYI2U3SkDfD3yS+h9sTlvdbJ1I0PssIM aabGjDXg7q6huCbsLq4IA7lQoIk1w4+kz2c0rZLv5wccD7ej+zjyIxxdADZApsLmD6eH nxd2X1sLTl2fuOoLqCZxSfwmvc8sVVuLUPVhWOHwZJfV0xBVYq0srD3WRcEhWkGwx7bm i45w== X-Gm-Message-State: AOAM531qDiWQ477MzHCCkT+SFK2DXGZMEokMW9rGpirx+araB5kBWZ0v j484qHrhL2pnJqxbrjQpR/cWHNSsCY8/1XdFWFXRZw== X-Google-Smtp-Source: ABdhPJzC75wfVv7uDBx7FFZZueGRerUzOktFsOTVm3DER7Jawg1I0FAq6BvQx2aO0pyLrFdGCptb2kUfExFAov3plvo= X-Received: by 2002:a05:6512:3f0d:b0:448:2ef2:ebe2 with SMTP id y13-20020a0565123f0d00b004482ef2ebe2mr1409857lfa.128.1646870466953; Wed, 09 Mar 2022 16:01:06 -0800 (PST) MIME-Version: 1.0 References: <20220308213417.1407042-1-zokeefe@google.com> <20220308213417.1407042-8-zokeefe@google.com> In-Reply-To: From: "Zach O'Keefe" Date: Wed, 9 Mar 2022 16:00:29 -0800 Message-ID: Subject: Re: [RFC PATCH 07/14] mm/khugepaged: add vm_flags_ignore to hugepage_vma_revalidate_pmd_count() To: Yang Shi Cc: Alex Shi , David Hildenbrand , David Rientjes , Michal Hocko , Pasha Tatashin , SeongJae Park , Song Liu , Vlastimil Babka , Zi Yan , Linux MM , Andrea Arcangeli , Andrew Morton , Arnd Bergmann , Axel Rasmussen , Chris Kennelly , Chris Zankel , Helge Deller , Hugh Dickins , Ivan Kokshaysky , "James E.J. Bottomley" , Jens Axboe , "Kirill A. Shutemov" , Matthew Wilcox , Matt Turner , Max Filippov , Miaohe Lin , Minchan Kim , Patrick Xia , Pavel Begunkov , Peter Xu , Thomas Bogendoerfer Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 18DCC180011 X-Rspam-User: Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=jiHj2JDx; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf16.hostedemail.com: domain of zokeefe@google.com designates 209.85.167.43 as permitted sender) smtp.mailfrom=zokeefe@google.com X-Stat-Signature: hnsdrrjymi5myfc5i8u5hhokmck5hjqg X-HE-Tag: 1646870468-372385 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 Tue, Mar 8, 2022 at 1:35 PM Zach O'Keefe wrote: > > > > In madvise collapse context, we optionally want to be able to ignore > > advice from MADV_NOHUGEPAGE-marked regions. > > Could you please elaborate why this usecase is valid? Typically > MADV_NOHUGEPAGE is set when the users really don't want to have THP > for this area. So it doesn't make too much sense to ignore it IMHO. > Hey Yang, thanks for taking time to review and comment. Semantically, the way I see it, is that MADV_NOHUGEPAGE is a way for the user to say "I don't want hugepages here", so that the kernel knows not to do so when faulting memory, and khugepaged can stay away. However, in MADV_COLLAPSE, the user is explicitly requesting this be backed by hugepages - so presumably that is exactly what they want. IOW, if the user didn't want this memory to be backed by hugepages, they wouldn't be MADV_COLLAPSE'ing it. If there was a range of memory the user wanted collapsed, but that had some sub-areas marked MADV_NOHUGEPAGE, they could always issue multiple MADV_COLLAPSE operations around the excluded regions. In terms of use cases, I don't have a concrete example, but a user could hypothetically choose to exclude regions from management from khugepaged, but still be able to collapse the memory themselves, when/if they deem appropriate. > > > > Add a vm_flags_ignore argument to hugepage_vma_revalidate_pmd_count() > > which can be used to ignore vm flags used when considering thp > > eligibility. > > > > Signed-off-by: Zach O'Keefe > > --- > > mm/khugepaged.c | 18 ++++++++++++------ > > 1 file changed, 12 insertions(+), 6 deletions(-) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index 1d20be47bcea..ecbd3fc41c80 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -964,10 +964,14 @@ khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) > > #endif > > > > /* > > - * Revalidate a vma's eligibility to collapse nr hugepages. > > + * Revalidate a vma's eligibility to collapse nr hugepages. vm_flags_ignore > > + * can be used to ignore certain vma_flags that would otherwise be checked - > > + * the principal example being VM_NOHUGEPAGE which is ignored in madvise > > + * collapse context. > > */ > > static int hugepage_vma_revalidate_pmd_count(struct mm_struct *mm, > > unsigned long address, int nr, > > + unsigned long vm_flags_ignore, > > struct vm_area_struct **vmap) > > { > > struct vm_area_struct *vma; > > @@ -986,7 +990,7 @@ static int hugepage_vma_revalidate_pmd_count(struct mm_struct *mm, > > hend = vma->vm_end & HPAGE_PMD_MASK; > > if (address < hstart || (address + nr * HPAGE_PMD_SIZE) > hend) > > return SCAN_ADDRESS_RANGE; > > - if (!hugepage_vma_check(vma, vma->vm_flags)) > > + if (!hugepage_vma_check(vma, vma->vm_flags & ~vm_flags_ignore)) > > return SCAN_VMA_CHECK; > > /* Anon VMA expected */ > > if (!vma->anon_vma || vma->vm_ops) > > @@ -1000,9 +1004,11 @@ static int hugepage_vma_revalidate_pmd_count(struct mm_struct *mm, > > */ > > > > static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, > > + unsigned long vm_flags_ignore, > > struct vm_area_struct **vmap) > > { > > - return hugepage_vma_revalidate_pmd_count(mm, address, 1, vmap); > > + return hugepage_vma_revalidate_pmd_count(mm, address, 1, > > + vm_flags_ignore, vmap); > > } > > > > /* > > @@ -1043,7 +1049,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, > > /* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */ > > if (ret & VM_FAULT_RETRY) { > > mmap_read_lock(mm); > > - if (hugepage_vma_revalidate(mm, haddr, &vma)) { > > + if (hugepage_vma_revalidate(mm, haddr, VM_NONE, &vma)) { > > /* vma is no longer available, don't continue to swapin */ > > trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); > > return false; > > @@ -1200,7 +1206,7 @@ static void collapse_huge_page(struct mm_struct *mm, > > count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); > > > > mmap_read_lock(mm); > > - result = hugepage_vma_revalidate(mm, address, &vma); > > + result = hugepage_vma_revalidate(mm, address, VM_NONE, &vma); > > if (result) { > > mmap_read_unlock(mm); > > goto out_nolock; > > @@ -1232,7 +1238,7 @@ static void collapse_huge_page(struct mm_struct *mm, > > */ > > mmap_write_lock(mm); > > > > - result = hugepage_vma_revalidate(mm, address, &vma); > > + result = hugepage_vma_revalidate(mm, address, VM_NONE, &vma); > > if (result) > > goto out_up_write; > > /* check if the pmd is still valid */ > > -- > > 2.35.1.616.g0bdcbb4464-goog > >