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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 Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=qbWXnTqL; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf18.hostedemail.com: domain of naoya.horiguchi@linux.dev designates 94.23.1.103 as permitted sender) smtp.mailfrom=naoya.horiguchi@linux.dev X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 182EF1C0009 X-Rspam-User: X-Stat-Signature: 7ppufn4ced3jrnzdbuy71mip4i9sowjf X-HE-Tag: 1651827558-485774 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 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 >