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Wed, 17 Sep 2025 16:38:05 +0300 (MSK) Received: from T-EXCH-12.corp.yadro.com (10.34.9.214) by T-EXCH-10.corp.yadro.com (10.34.9.212) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.9; Wed, 17 Sep 2025 16:38:05 +0300 Received: from yadro.com (172.17.34.51) by T-EXCH-12.corp.yadro.com (10.34.9.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.12; Wed, 17 Sep 2025 16:38:04 +0300 Date: Wed, 17 Sep 2025 16:38:04 +0300 From: Dmitry Bogdanov To: Mike Christie CC: , , , Subject: Re: [PATCH v2 3/3] scsi: target: Move LUN stats to per CPU Message-ID: <20250917133804.GF624@yadro.com> References: <20250908231000.10777-1-michael.christie@oracle.com> <20250908231000.10777-4-michael.christie@oracle.com> Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250908231000.10777-4-michael.christie@oracle.com> X-ClientProxiedBy: RTM-EXCH-01.corp.yadro.com (10.34.9.201) To T-EXCH-12.corp.yadro.com (10.34.9.214) X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 2.1.1.8310, bases: 2025/09/17 12:43:00 #27827050 X-KSMG-AntiVirus-Status: NotDetected, skipped X-KSMG-KATA-Status: Not Scanned X-KSMG-LinksScanning: NotDetected X-KSMG-Message-Action: skipped X-KSMG-Rule-ID: 5 On Mon, Sep 08, 2025 at 06:05:56PM -0500, Mike Christie wrote: > > The atomic use in the main I/O path is causing perf issues when using > higher performance backend devices and multiple queues (more than > 10 when using vhost-scsi) like with this fio workload: > > [global] > bs=4K > iodepth=128 > direct=1 > ioengine=libaio > group_reporting > time_based > runtime=120 > name=standard-iops > rw=randread > numjobs=16 > cpus_allowed=0-15 > > To fix this issue, this moves the LUN stats to per CPU. > > Note: I forgot to include this patch with the delayed/ordered per CPU > tracking and per device/device entry per CPU stats. With this patch you > get the full 33% improvements when using fast backends, multiple queues > and multiple IO submiters. > > Signed-off-by: Mike Christie Reviewed-by: Dmitry Bogdanov