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Tue, 14 Nov 2023 19:15:57 -0800 (PST) From: xu X-Google-Original-From: xu To: david@redhat.com Cc: akpm@linux-foundation.org, imbrenda@linux.ibm.com, jiang.xuexin@zte.com.cn, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ran.xiaokai@zte.com.cn, wang.yong12@zte.com.cn, xu.xin.sc@gmail.com, xu.xin16@zte.com.cn, yang.yang29@zte.com.cn Subject: Re: [PATCH] ksm: delay the check of splitting compound pages Date: Wed, 15 Nov 2023 03:15:53 +0000 Message-Id: <20231115031553.1970634-1-xu.xin16@zte.com.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <938be193-8a73-432e-b424-53afa9f8c38e@redhat.com> References: <938be193-8a73-432e-b424-53afa9f8c38e@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: F0749180003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 4a6fqis495zhxw6dx6ffqrd9jjrrz56n X-HE-Tag: 1700018159-937936 X-HE-Meta: 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 ubxcblLB 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000011, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> From: xu xin >> >> Background >> ========== >> When trying to merge two pages, it may fail because the two pages >> belongs to the same compound page and split_huge_page fails due to >> the incorrect reference to the page. To solve the problem, the commit >> 77da2ba0648a4 ("mm/ksm: fix interaction with THP") tries to split the >> compound page after try_to_merge_two_pages() fails and put_page in >> that case. However it is too early to calculate of the variable 'split' which >> indicates whether the two pages belongs to the same compound page. >> >> What to do >> ========== >> If try_to_merge_two_pages() succeeds, there is no need to check whether >> to splitting compound pages. So we delay the check of splitting compound >> pages until try_to_merge_two_pages() fails, which can improve the >> processing efficiency of cmp_and_merge_page() a little. >> >> Signed-off-by: xu xin >> Reviewed-by: Yang Yang > >Can we please add a unit test to ksm_functional_tests.c so we actually >get it right this time? Sure. Maybe we can simply refer to the reproducing way Claudio proposes in 77da2ba0648a4 ("mm/ksm: fix interaction with THP"). >-- >Cheers, > >David / dhildenb