Re: [PATCH 0/2] x86: Speed up ioremap operations

From: Andrew Morton
Date: Wed Aug 27 2014 - 19:20:14 EST


On Wed, 27 Aug 2014 16:15:28 -0700 Mike Travis <travis@xxxxxxx> wrote:

>
> >
> >> There are two causes for requiring a restart/reload of the drivers.
> >> First is periodic preventive maintenance (PM) and the second is if
> >> any of the devices experience a fatal error. Both of these trigger
> >> this excessively long delay in bringing the system back up to full
> >> capability.
> >>
> >> The problem was tracked down to a very slow IOREMAP operation and
> >> the excessively long ioresource lookup to insure that the user is
> >> not attempting to ioremap RAM. These patches provide a speed up
> >> to that function.
> >
> > With what result?
> >
>
> Early measurements on our in house lab system (with far fewer cpus
> and memory) shows about a 60-75% increase. They have a 31 devices,
> 3000+ cpus, 10+Tb of memory. We have 20 devices, 480 cpus, ~2Tb of
> memory. I expect their ioresource list to be about 5-10 times longer.
> [But their system is in production so we have to wait for the next
> scheduled PM interval before a live test can be done.]

So you expect 1+ hours? That's still nuts.
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