sync with openbsd-current
sync with openbsd-current
sync with openbsd-current
Merge branch 'master' into hellfish
sync with openbsd-current
Subject:
Re: page zeroing
From:
Mark Kettenis <mark.kettenis@xs4all.nl>
Date:
09/27/2014 10:33 AM
To:
tech@openbsd.org

> > Date: Fri, 26 Sep 2014 21:01:38 +0200 (CEST)
> > From: Mark Kettenis <mark.kettenis@xs4all.nl>
> >
> > The diff below adds a kernel thread that makes memory pages filled
> > with zeroes without olding the kernel lock.  The idea is that this
> > should speed up MP systems because the kernel can do some useful work
> > in parallel with other things, and could lower the latency on all
> > systems because (userland) memory page allocation will be faster.  The
> > thread runs at the absolutely lowest priority such that we only run it
> > if we don't have anything else to do.
> >
> > But this could also slow down some systems though, because zeroing
> > pages can thrash the caches in your system.
> >
> > So I'd like to see this diff tested on a wide variety of systems, and
> > hear back from people how this diff affects their OpenBSD systems.
> > Subjective reports are ok; hard benchmarks are better.
> >
> > One thing to look at when you're running this diff is the output of
> > "vmstat -s".  It will report something like:
> >
> >     2146380 zeroed page hits
> >       34258 zeroed page misses
> >
> > You want the number of hits to be significantly larger than the number
> > of misses.  And you want the number of hits to keep growing.  Another
> > thing to look at is "systat vm".  If you mke your screen a bit bigger
> > than 25 lines, you'll see a "pzidle" counter which indicates how much
> > zeroed pages have been consumed (negative) or created (positive).
> >
> > Thanks,
> >
> > Mark
Merge branch 'hellfish' of https://github.com/netzbasis/openbsd-src into hellfish
Merge branch 't-page_zeroing' into hellfish