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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fc0bc4656dsm81461375ad.258.2024.07.17.18.27.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Jul 2024 18:27:44 -0700 (PDT) Date: Wed, 17 Jul 2024 15:27:43 -1000 From: "tj@kernel.org" To: Boy Wu =?utf-8?B?KOWQs+WLg+iqvCk=?= Cc: "linux-kernel@vger.kernel.org" , "boris@bur.io" , "linux-block@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , "cgroups@vger.kernel.org" , "axboe@kernel.dk" , Iverlin Wang =?utf-8?B?KOeOi+iLs+mclik=?= , "josef@toxicpanda.com" , "linux-arm-kernel@lists.infradead.org" , "matthias.bgg@gmail.com" , "angelogioacchino.delregno@collabora.com" Subject: Re: [PATCH v3] blk-cgroup: Replace u64 sync with spinlock for iostat update Message-ID: References: <20240716075206.23121-1-boy.wu@mediatek.com> <5560c690cc6de67139a9b2e45c7a11938b70fc58.camel@mediatek.com> <1b19b68adb34410bf6dc8fd3f50e4b82c1a014e4.camel@mediatek.com> <99af713e187a92f0501482e8344be469f1b3e454.camel@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <99af713e187a92f0501482e8344be469f1b3e454.camel@mediatek.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240717_182746_688008_B8D44DF7 X-CRM114-Status: GOOD ( 10.33 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org Hello, On Thu, Jul 18, 2024 at 01:21:32AM +0000, Boy Wu (吳勃誼) wrote: ... > I think this will work, but as I mentioned before, this issue is only > on 32 bit SMP systems. Replacing u64 sync with spinlock will increase > overhead on 64 bit systems, because u64 sync does nothing on 64 bit > systems. However, if it is acceptable, we can proceed with this > solution. We can encapsulate the spinlock in some helpers and make them conditional on 32bit. However, the u64_sync -> spinlock conversions in the suggested patch are all on cold paths, so I doubt it'd be all that noticeable especially given that the hottest path of them all is already grabbing blkg_stat_lock, but either way is fine by me. Thanks. -- tejun