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[193.116.97.30]) by smtp.gmail.com with ESMTPSA id a23sm11625185pjh.19.2020.12.19.21.03.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Dec 2020 21:03:51 -0800 (PST) From: Nicholas Piggin To: linux-mm@kvack.org Cc: Nicholas Piggin , Peter Zijlstra Subject: [PATCH 3/3] mm: skip page_cpupid_reset_last atomic update if the value is already reset Date: Sun, 20 Dec 2020 15:03:40 +1000 Message-Id: <20201220050340.849754-3-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20201220050340.849754-1-npiggin@gmail.com> References: <20201220050340.849754-1-npiggin@gmail.com> MIME-Version: 1.0 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: Improves performance of a PROT_READ -> PROT_READ|PROT_WRITE -> store microbenchmark (which goes via the wp_page_reuse fault path) by about 10% on a POWER9. Signed-off-by: Nicholas Piggin --- include/linux/mm.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6ece500464e0..c0a9e8de0738 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1382,6 +1382,9 @@ static inline void __page_cpupid_reset_last(struct page *page) static inline void page_cpupid_reset_last(struct page *page) { + if (page_cpupid_last(page) == (-1 & LAST_CPUPID_MASK)) + return; + page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1); }