From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 Date: Wed, 31 Jan 2018 11:43:33 -0700 From: Scotty Bauer To: Ming Lei Subject: Re: [LSF/MM TOPIC] KPTI effect on IO performance In-Reply-To: <20180131082331.GA25888@ming.t460p> References: <20180131082331.GA25888@ming.t460p> Message-ID: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-block@vger.kernel.org, lsf-pc@lists.linux-foundation.org, linux-nvme@lists.infradead.org, Linux-scsi@vger.kernel.org Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+axboe=kernel.dk@lists.infradead.org List-ID: On 2018-01-31 01:23, Ming Lei wrote: > Hi All, > > After KPTI is merged, there is extra load introduced to context switch > between user space and kernel space. It is observed on my laptop that > one > syscall takes extra ~0.15us[1] compared with 'nopti'. > > IO performance is affected too, it is observed that IOPS drops by 32% > in > my test[2] on null_blk compared with 'nopti': > > randread IOPS on latest linus tree: > ------------------------------------------------- > | randread IOPS | randread IOPS with 'nopti'| > ------------------------------------------------ > | 928K | 1372K | > ------------------------------------------------ > > Do you know if your CPU has PCID? It would be interesting to see these tests on older CPUs or older kernels without PCID support. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme