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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3809C433F5 for ; Fri, 6 May 2022 08:59:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1390321AbiEFJDM (ORCPT ); Fri, 6 May 2022 05:03:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232076AbiEFJDJ (ORCPT ); Fri, 6 May 2022 05:03:09 -0400 Received: from out0.migadu.com (out0.migadu.com [IPv6:2001:41d0:2:267::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A524963519 for ; Fri, 6 May 2022 01:59:27 -0700 (PDT) Date: Fri, 6 May 2022 17:59:20 +0900 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1651827566; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=P1HmSJWhSIX/xlEGz2iSAB8cx2SMZp3jJMtDuWQ7g48=; b=qbWXnTqLPh4emRaNAmRy/km7pAH8zEjTqbINWktwnWEh5ztCr6xwox9qQ7kOGRElD7BnZz 1WK41tAKl75yoHSrJJE0aofwtfubEIjIGcbuIx0PmFJg2e/DOW1CKfDB+uSLlmka4Wcgax h7bjWAhZ97wBNl6hMSbhAFSG2IJkqhE= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Naoya Horiguchi To: zhenwei pi Cc: akpm@linux-foundation.org, naoya.horiguchi@nec.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wu Fengguang Subject: Re: [PATCH 3/4] mm/memofy-failure.c: optimize hwpoison_filter Message-ID: <20220506085920.GC1356094@u2004> References: <20220429142206.294714-1-pizhenwei@bytedance.com> <20220429142206.294714-4-pizhenwei@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220429142206.294714-4-pizhenwei@bytedance.com> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 29, 2022 at 10:22:05PM +0800, zhenwei pi wrote: > In the memory failure procedure, hwpoison_filter has higher priority, > if memory_filter() filters the error event, there is no need to do > the further work. Could you clarify what problem you are trying to solve (what does "optimize" mean in this context or what is the benefit)? Now hwpoison_filter() can be called both with *and* without taking page refcount. It's mainly called *with* taking page refcount in order to make sure that the actual handling process is executed only for pages that meet a given condition. IOW, it's important to prevent pages which do not meet the condition from going ahead to further steps (false-positive is not permitted). So this type of callsite should not be omittable. As for the other case, hwpoison_filter() is also called in hwpoison_inject() *without* taking page refcount. This actually has a different nuance and intended to speculatively filter the injection events before setting PageHWPoison flag to reduce the noise due to setting PG_hwpoison temporary. The point is that it's not intended here to filter precisely and this callsite is omittable. So in my understanding, we need keep hwpoison_filter() after taking page refcount as we do now. Maybe optionally and additionally calling hwpoison_filter() at the beginning of memory_failure() might be possible, but I'm not sure yet how helpful... Thanks, Naoya Horiguchi > > Cc: Wu Fengguang > Signed-off-by: zhenwei pi > --- > mm/memory-failure.c | 14 +++++--------- > 1 file changed, 5 insertions(+), 9 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index ece05858568f..a6a27c8b800f 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1800,6 +1800,11 @@ int memory_failure(unsigned long pfn, int flags) > goto unlock_mutex; > } > > + if (hwpoison_filter(p)) { > + res = -EOPNOTSUPP; > + goto unlock_mutex; > + } > + > try_again: > res = try_memory_failure_hugetlb(pfn, flags, &hugetlb); > if (hugetlb) > @@ -1937,15 +1942,6 @@ int memory_failure(unsigned long pfn, int flags) > */ > page_flags = p->flags; > > - if (hwpoison_filter(p)) { > - if (TestClearPageHWPoison(p)) > - num_poisoned_pages_dec(); > - unlock_page(p); > - put_page(p); > - res = -EOPNOTSUPP; > - goto unlock_mutex; > - } > - > /* > * __munlock_pagevec may clear a writeback page's LRU flag without > * page_lock. We need wait writeback completion for this page or it > -- > 2.20.1 >