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d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=G999qRJ3ZYDAwyPJfqHMd90vcXhx8IHao6Ql7QiFPDQ=; b=uJkjTmS/DQQxCw2SN8INhfYsAB1R53cL+xxjCJPdEMsvlOnmEf6UwlN9GlATCXH1MH 32/IAb1MQ0Ldp4UAnmMj6sxCF8P7c5DX1zXnucb3kXOXrHZP5DmVYWFCfxaqXTMsd4Jh eTxCDUwB11iScM79WTMp+qkLGk8VQwv5IY4I3uv+eejzHqBIJnkcyMz7WVVdqQ1EG02b zdMjzEU+eSkF5Re1VUEWY3J4gLJMJsQK2pm3uI5WDrTXCFiCl49G1L1pMRpRmEqFzxtm F+j3XsOkYou0QOp0Y0JpYzSVUn5KD29i4bHFAvXk2S53gtPCERzpp9BuszigkcO1bPKt HZdQ== X-Gm-Message-State: ACrzQf0Z7JqSp/EoGjylhu7X4YjC1gvBPSdfD71XNhq5hzkIPFCqDnp6 uGtuVttEbglrlH36Ig9XgpYf1X87Iaok8i6TVC4= X-Google-Smtp-Source: AMsMyM6UiGVnTD/J8ryFZQsJHTbdkIhpQZQxOdBwdC1toRqikXsXkHg47dV0ojfdIgLd8MUR/GxUavW0TPpgHSHF44M= X-Received: by 2002:aa7:cb87:0:b0:43b:e650:6036 with SMTP id r7-20020aa7cb87000000b0043be6506036mr18386887edt.350.1663645189918; Mon, 19 Sep 2022 20:39:49 -0700 (PDT) MIME-Version: 1.0 References: <20220822082120.8347-1-yangyicong@huawei.com> <20220822082120.8347-5-yangyicong@huawei.com> <302febae-508c-d73e-8676-d51752946645@arm.com> In-Reply-To: <302febae-508c-d73e-8676-d51752946645@arm.com> From: Barry Song <21cnbao@gmail.com> Date: Tue, 20 Sep 2022 15:39:38 +1200 Message-ID: Subject: Re: [PATCH v3 4/4] arm64: support batched/deferred tlb shootdown during page reclamation To: Anshuman Khandual Cc: Yicong Yang , akpm@linux-foundation.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, catalin.marinas@arm.com, will@kernel.org, linux-doc@vger.kernel.org, corbet@lwn.net, peterz@infradead.org, arnd@arndb.de, linux-kernel@vger.kernel.org, darren@os.amperecomputing.com, yangyicong@hisilicon.com, huzhanyuan@oppo.com, lipeifeng@oppo.com, zhangshiming@oppo.com, guojian@oppo.com, realmz6@gmail.com, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, wangkefeng.wang@huawei.com, xhao@linux.alibaba.com, prime.zeng@hisilicon.com, Barry Song , Nadav Amit , Mel Gorman Content-Type: text/plain; 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dkim=pass header.d=gmail.com header.s=20210112 header.b=a1adS1EC; spf=pass (imf21.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.208.49 as permitted sender) smtp.mailfrom=21cnbao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: rygqmtr1nsjfxgrwjeqm4w9ik7n6skwu X-HE-Tag: 1663645191-305525 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 Tue, Sep 20, 2022 at 3:00 PM Anshuman Khandual wrote: > > > On 8/22/22 13:51, Yicong Yang wrote: > > +static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm) > > +{ > > + return true; > > +} > > This needs to be conditional on systems, where there will be performance > improvements, and should not just be enabled all the time on all systems. > num_online_cpus() > X, which does not hold any cpu hotplug lock would be > a good metric ? for a small system, i don't see how this patch will help, e.g. cpus <= 4; so we can actually disable tlb-batch on small systems. just need to check if we will have any race condition since hotplug will make the condition true and false dynamically. Thanks Barry