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[58.6.239.121]) by smtp.gmail.com with ESMTPSA id x67sm19601345pfx.144.2021.03.16.23.47.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Mar 2021 23:47:47 -0700 (PDT) From: Nicholas Piggin To: linux-mm@kvack.org Cc: Nicholas Piggin , Peter Zijlstra Subject: [PATCH v2 3/3] mm: skip page_cpupid_reset_last atomic update if the value is already reset Date: Wed, 17 Mar 2021 16:47:30 +1000 Message-Id: <20210317064730.546507-3-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20210317064730.546507-1-npiggin@gmail.com> References: <20210317064730.546507-1-npiggin@gmail.com> MIME-Version: 1.0 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 357D3E0001AF X-Stat-Signature: x3anzrdn6ztyfdets4fggoq75kyxbdzm Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf13; identity=mailfrom; envelope-from=""; helo=mail-pg1-f179.google.com; client-ip=209.85.215.179 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615963669-119965 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 2524553ea898..1e1471235055 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1420,6 +1420,9 @@ 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); }