Re: [PATCH RFC V2 3/3] scsi_mq: enable runtime PM

Johannes Thumshirn
2018-07-19T06:41:24Z

On Wed, Jul 18, 2018 at 11:01:52AM -0400, Alan Stern wrote:
> On Wed, 18 Jul 2018, Johannes Thumshirn wrote:
>
> > On Wed, Jul 18, 2018 at 10:12:37AM -0400, Alan Stern wrote:
> > > As one extra reminder... People who care about extreme performance can
> > > perfectly well disable CONFIG_PM in their kernels. That should remove
> > > any overhead due to runtime PM.
> >
> > Yes but how likely is this for people who are running their data
> > center with a distribution kernel.
>
> Strictly speaking, that's a nonsense question. People who run
> distribution kernels are 100% unlikely to change the kernel
> configuration, by definition.
>
> That's not the point. If people really care about getting the utmost
> performance, to the extent that they resent the minimal overhead
> required for runtime PM, then they should not be running distribution
> kernels in the first place.

Can we agree to disagree here?

Some of the people I know in HPC, HFT, etc... run stock SLE/RHEL and
they do file bugs for every single 3-5% performance regression. This
is not something I made up, this is the kind of things I have to deal
with on my day job.

So long,
Johannes
--
Johannes Thumshirn Storage
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