From: Scotty Bauer <sbauer@eng.utah.edu>
To: Ming Lei <ming.lei@redhat.com>
Cc: linux-block@vger.kernel.org, lsf-pc@lists.linux-foundation.org,
linux-nvme@lists.infradead.org, Linux-scsi@vger.kernel.org
Subject: Re: [LSF/MM TOPIC] KPTI effect on IO performance
Date: Wed, 31 Jan 2018 11:43:33 -0700 [thread overview]
Message-ID: <d6729ac299e153de259cb8f8af0c888b@eng.utah.edu> (raw)
In-Reply-To: <20180131082331.GA25888@ming.t460p>
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.
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next prev parent reply other threads:[~2018-01-31 18:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-31 8:23 [LSF/MM TOPIC] KPTI effect on IO performance Ming Lei
2018-01-31 18:43 ` Scotty Bauer [this message]
2018-02-01 2:35 ` [Lsf-pc] " Ming Lei
2018-02-01 3:05 ` Ming Lei
2018-02-01 21:51 ` Bart Van Assche
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