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Thu, 14 Nov 2024 07:14:13 -0800 (PST) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-71a6eb73b60sm413694a34.68.2024.11.14.07.14.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Nov 2024 07:14:12 -0800 (PST) Message-ID: <0236980b-b892-460c-802e-a87a79b7ac0b@kernel.dk> Date: Thu, 14 Nov 2024 08:14:11 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: don't reorder requests passed to ->queue_rqs To: Christoph Hellwig Cc: Chaitanya Kulkarni , "Michael S. Tsirkin" , Jason Wang , Keith Busch , Sagi Grimberg , Pavel Begunkov , "linux-block@vger.kernel.org" , "virtualization@lists.linux.dev" , "linux-nvme@lists.infradead.org" , "io-uring@vger.kernel.org" References: <20241113152050.157179-1-hch@lst.de> <2f7fa13a-71d9-4a8d-b8f4-5f657fdaab60@kernel.dk> <20241114041603.GA8971@lst.de> Content-Language: en-US From: Jens Axboe In-Reply-To: <20241114041603.GA8971@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241114_151617_496929_B089FA3B X-CRM114-Status: GOOD ( 18.87 ) X-BeenThere: linux-nvme@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-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 11/13/24 9:16 PM, Christoph Hellwig wrote: > On Wed, Nov 13, 2024 at 01:51:48PM -0700, Jens Axboe wrote: >> Thanks for testing, but you can't verify any kind of perf change with >> that kind of setup. I'll be willing to bet that it'll be 1-2% drop at >> higher rates, which is substantial. But the reordering is a problem, not >> just for zoned devices, which is why I chose to merge this. > > So I did not see any variation, but I also don't have access to a really > beefy setup right now. If there is a degradation it probably is that > touching rq_next for each request actually has an effect if the list is > big enough and they aren't cache hot any more. I can cook up a patch Exactly. > that goes back to the scheme currently used upstream in nvme and virtio > that just cuts of the list at a hctx change instead of moving the > requests one by one now that the block layer doesn't mess up the order. I think that would be useful. I can test. -- Jens Axboe