Hi
On Wednesday 19 February 2014, Greg KH wrote:
> On Wed, Feb 19, 2014 at 10:37:26PM +0000, Stefan Lippers-Hollmann wrote:
> > Hi
> >
> > On Wednesday 19 February 2014, [email protected] wrote:
> > > From: Dirk Brandewie <[email protected]>
> > >
> > > Take non-idle time into account when calculating core busy time.
> > > This ensures that intel_pstate will notice a decrease in load.
> > >
> > > backport of commit: fcb6a15c2e7e76d493e6f91ea889ab40e1c643a4
> > > Applies to v3.10.30, v3.12.11, v3.13.3
> > >
> > > References: https://bugzilla.kernel.org/show_bug.cgi?id=66581
> > > Cc: 3.10+ <[email protected]> # 3.10+
> > > Signed-off-by: Dirk Brandewie <[email protected]>
> >
> > After testing this patch, I can confirm that this revision of the patch
> > no longer crashes the kernel (tested on sandy-bridge and ivy-bridge),
> > thanks a lot.
>
> But does it slow it down? My machine has horrible build times with this
> patch installed on 3.14-rc2. Reverted, my builds go back to normal
> speeds (2 minutes instead of 8 minutes.)
[...]
By the time of my first response, I had just booted a new kernel with v2
of "intel_pstate: Take core C0 time into account for core busy
calculation" on a couple of systems, but hadn't done any benchmarks
yet. Now I've done some very preliminary benchmarks.
Benchmark environment:
Building v3.14.4-rc1 with a very modular, distro-like, configuration
for both amd64 and i686 within a buildd environment (Debian/ sid,
pbuilder). These figures include the overhead of the buildd environment
(unpacking the gzipped build chroot, installing the required build
dependencies (fetching from a local proxy server) into this chroot,
untarring (+ single threaded xz) the 3.13.0 tarball, applying the
patches (incl. patch-3.13.3+patch-3.13.4-rc1) and building the packages
(using single threaded xz for the package components). The systems have
been freshly rebooted for each test and are otherwise close to idle,
the build concurrency has been set to 16.
system A (sandy-bridge):
build host running 3.13.4-rc1 without any revision of this patch applied
real 27m35.298s
user 177m28.016s
sys 13m54.164s
build host running 3.13.4-rc1 with revision 2 of this patch applied
real 28m3.600s
user 177m59.199s
sys 14m11.025s
system B (ivy-bridge):
build host running 3.13.4-rc1 without any revision of this patch applied
real 24m51.323s
user 156m0.813s
sys 12m22.535s
build host running 3.13.4-rc1 with revision 2 of this patch applied
real 25m20.189s
user 157m44.803s
sys 12m46.669s
Each test has only been done once, so I'm not calling this a scientific
or representative benchmark yet, but the delta is similar on both
systems - slightly, but not massively, worse with this patch applied.
Regards
Stefan Lippers-Hollmann
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