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=-8.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 B9101C3F68F for ; Thu, 9 Jan 2020 12:32:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B48E2077B for ; Thu, 9 Jan 2020 12:32:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="GdGm/gg9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730949AbgAIMcg (ORCPT ); Thu, 9 Jan 2020 07:32:36 -0500 Received: from mail-lf1-f67.google.com ([209.85.167.67]:43011 "EHLO mail-lf1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729237AbgAIMcg (ORCPT ); Thu, 9 Jan 2020 07:32:36 -0500 Received: by mail-lf1-f67.google.com with SMTP id 9so5062150lfq.10 for ; Thu, 09 Jan 2020 04:32:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=dNz1YuP2AfKv0aZ9saeylvptSi351fPnO7qobVoMRPk=; b=GdGm/gg9gF45ctnIoiAyLlkYKo33jPT+zrPTv/pl2hZZ6QaHmJO21KrwGt9KvHGEPL //3gnS3w08b6zS0fqIkZcsw+5+z208KqUol6784i8GL/QEg+CwD7bGpWP8TKHNMEw3AT kitiLOeLTZOAAh9T6yv1uyFzyKsQdxBfd6i86nW/UbbqsD7b6UUmtBXDvtT5mXGYgnjQ ie+iZLuLh5X8YOp+QYnqkj7ZD2iLV7FCRda9ffCMsV5hoZzIuJ9FSyMF7JvM/ufUUT0q SqWgIvk6mXNh40JIkwcoh0gH+Lu3Abav4EJh5zXCjUcvALpxwPLOQUKTuFBvi5WPYaMe lxjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=dNz1YuP2AfKv0aZ9saeylvptSi351fPnO7qobVoMRPk=; b=kMBgiRInHhq2Bxed6Ww080q2VuGdyNsodCUQXeUgOi87WWaXrzqpSNI2xL6NOAJQWm 3owBLQqM3VP95f+XJsV4UwYsy95Z5YZG3i9trTXefZHMTUPxcX2ebJWnXlI9NI++m1li wsfZWSG1hjvz8krI9knR7uzkXhUAe6otCnC4hD/VdEu2kWP9Y4HTGF3ug/8x7L/5P+op sOrs8TbfPxi5bH10/JUzVAm8G517w+UJ1FVFqGqnOy5Ol97P6ZEO39mfVWoSs9yc/w33 xalueg6DIzo+qiQZUQLQDqWD5tzJ8TNyjyuZ4iU2mM7dw7NLAAlNirHAevfuaUXAUVur C7gQ== X-Gm-Message-State: APjAAAVd1jBH4h3WI7C8CmAfOduwdZ8+FnSS8HDxsPxy3G4QkgUukOc2 TBtPysgEdca2t9oqfrWzLq3deg== X-Google-Smtp-Source: APXvYqwcL80LZwTLfyb+q6lO6S1d/bO/4ZzrS9E/1X9t7wr0uSPvxZEh1sXI5zuaBEWWE9Xv5oU83Q== X-Received: by 2002:ac2:5dc7:: with SMTP id x7mr6079826lfq.24.1578573154370; Thu, 09 Jan 2020 04:32:34 -0800 (PST) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id b19sm3000589ljk.25.2020.01.09.04.32.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2020 04:32:33 -0800 (PST) Received: by box.localdomain (Postfix, from userid 1000) id 7095B1007DB; Thu, 9 Jan 2020 15:32:33 +0300 (+03) Date: Thu, 9 Jan 2020 15:32:33 +0300 From: "Kirill A. Shutemov" To: Wei Yang Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, richard.weiyang@gmail.com Subject: Re: [RFC PATCH] mm/rmap.c: finer hwpoison granularity for PTE-mapped THP Message-ID: <20200109123233.ye2h4dxaubu4ad22@box> References: <20200102030421.30799-1-richardw.yang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200102030421.30799-1-richardw.yang@linux.intel.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 02, 2020 at 11:04:21AM +0800, Wei Yang wrote: > Currently we behave differently between PMD-mapped THP and PTE-mapped > THP on memory_failure. > > User detected difference: > > For PTE-mapped THP, the whole 2M range will trigger MCE after > memory_failure(), while only 4K range for PMD-mapped THP will. > > Direct reason: > > All the 512 PTE entry will be marked as hwpoison entry for a PTE-mapped > THP while only one PTE will be marked for a PMD-mapped THP. > > Root reason: > > The root cause is PTE-mapped page doesn't need to split pmd which skip > the SPLIT_FREEZE process. I don't follow how SPLIT_FREEZE is related to pisoning. Cold you laraborate? > This makes try_to_unmap_one() do its job when > the THP is not splited. And since page is HWPOISON, all the entries in > THP is marked as hwpoison entry. > > While for the PMD-mapped THP, SPLIT_FREEZE will save migration entry to > pte and this skip try_to_unmap_one() before THP splited. And then only > the affected 4k page is marked as hwpoison entry. > > This patch tries to provide a finer granularity for PTE-mapped THP by > only mark the affected subpage as hwpoison entry when THP is not > split. > > Signed-off-by: Wei Yang > > --- > This complicates the picture a little, while I don't find a better way to > improve. > > Also I may miss some case or not handle this properly. > > Look forward your comments. > --- > mm/rmap.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index b3e381919835..90229917dd64 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1554,10 +1554,11 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > set_huge_swap_pte_at(mm, address, > pvmw.pte, pteval, > vma_mmu_pagesize(vma)); > - } else { > + } else if (!PageAnon(page) || page == subpage) { > dec_mm_counter(mm, mm_counter(page)); > set_pte_at(mm, address, pvmw.pte, pteval); > - } > + } else > + goto freeze; > > } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) { > /* > @@ -1579,6 +1580,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > swp_entry_t entry; > pte_t swp_pte; > > +freeze: > if (arch_unmap_one(mm, vma, address, pteval) < 0) { > set_pte_at(mm, address, pvmw.pte, pteval); > ret = false; > -- > 2.17.1 > > -- Kirill A. Shutemov