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Thu, 04 Jul 2024 07:36:51 +0000 Message-ID: <9de5d83c-4b05-4f69-8ab4-b4aa65e5ec62@suse.de> Date: Thu, 4 Jul 2024 09:36:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] nvme-tcp: per-controller I/O workqueues Content-Language: en-US To: Tejun Heo , Sagi Grimberg Cc: Hannes Reinecke , Christoph Hellwig , Keith Busch , linux-nvme@lists.infradead.org References: <20240703135021.34143-1-hare@kernel.org> <20240703135021.34143-2-hare@kernel.org> <7e4444d0-f156-439e-9363-4beb86bb6248@grimberg.me> From: Hannes Reinecke In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-4.29 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_FIVE(0.00)[6]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:email] X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240704_003653_987030_EC87AB1D X-CRM114-Status: GOOD ( 14.28 ) 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 7/3/24 21:17, Tejun Heo wrote: > Hello, > > On Wed, Jul 03, 2024 at 10:14:14PM +0300, Sagi Grimberg wrote: > ... >> None of these reasons are the claimed reason to use separate workqueues in >> this patch. The claim is that it is more efficient, i.e. has less overhead. >> >> The commit msg is the following: >> "Implement per-controller I/O workqueues to reduce workqueue contention >> during I/O." > > Hmm... it's not impossible for the concurrency accounting in pool_workqueues > to show up if the issue rate is *really* high but I'd be surprised if that > actually matters given that the backend pool is shared. Maybe I'm missing > something but I don't see a reason why multiple workqueues would be more > efficient than a shared one. > Well, I seem to run into the 'really high' issue rate case: unbound workqueue bound workqueue single wq multi wq single wq multi wq 4k seq read: 247MiB/s 249MiB/s 263MiB/s 365MiB/s 4k rand read: 294MiB/s 305MiB/s 279MiB/s 307MiB/s 4k seq write: 504MiB/s 499MiB/s 521MiB/s 550MiB/s 4k rand write: 531MiB/s 536MiB/s 476MiB/s 453MiB/s Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich