llvm dev - Mar 2018 - New LLD performance builder

Disabling swap and having a single CPU in the shield group didn't change
much, besides cpu-migrations and context-switches, which now are 0
obviously.
That clustering remains the same. It is also stable to the number of runs
(I have changed the test to run 20 times in the middle of that range on the
right).

http://lnt.llvm.org/db_default/v4/link/graph?highlight_run=426&plot.9=1.9.6

Unless somebody has a good idea what else we should try, it seems we have
it as good as it could be with the current approach.

Thanks

Galina


On Wed, Feb 28, 2018 at 2:16 PM, Galina Kistanova <gkistanova at
gmail.com>
wrote:
> >  The HT siblings are disabled, right?
>
> Correct.
>
> >  It is probably a good idea to experiment with disabling swap and
having
> > a single cpu in the shield group.
>
> Yep. This is what I'm in the middle of.
>
> So far I see that it seems the scheduler is keep running on shielded cores
> no matter what.
> Even if there is only 1 core in the shield.
>
> Thanks
>
> Galina
>
>
> On Wed, Feb 28, 2018 at 11:36 AM, Rafael Avila de Espindola <
> rafael.espindola at gmail.com> wrote:
>
>> Galina Kistanova <gkistanova at gmail.com> writes:
>>
>> > Yep. They are still clustered.
>> >
>> >>  Is there anything else running on the machine while the tests
are run?
>> >
>> > Not much. The usual buildslave stuff - buildbot, ssh server, some
light
>> > network services, snmp client, but that's pretty much it. 20
hardware
>> > threads are designated for this.
>> >
>> > The test runs on designated for tests only 10 CPUs shielded.
>> > There only perf and lld runs. All the obj files for the tests and
the
>> > linker itself are on tmpfs, so no disk I/O is involved. Swap file
is
>> > (almost) empty - few MBs is in use.
>> >
>> > It might be that different CPUs gets used for different test runs,
as
>> the
>> > script starts each run from the scratch. Just a guess. I will look
in to
>> > this closer.
>> > I'll take the bot off line to see if having perf running the
tests
>> multiple
>> > times would give a better result. And would try to reduce the
number of
>> > designated CPUs to see how that would affect the numbers as well.
>>
>> The HT siblings are disabled, right?
>>
>> It is probably a good idea to experiment with disabling swap and having
>> a single cpu in the shield group.
>>
>> Thanks,
>> Rafael
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20180312/842f0908/attachment.html>

Galina Kistanova <gkistanova at gmail.com> writes:
> Disabling swap and having a single CPU in the shield group didn't
change
> much, besides cpu-migrations and context-switches, which now are 0
> obviously.
> That clustering remains the same. It is also stable to the number of runs
> (I have changed the test to run 20 times in the middle of that range on the
> right).
>
>
http://lnt.llvm.org/db_default/v4/link/graph?highlight_run=426&plot.9=1.9.6
>
> Unless somebody has a good idea what else we should try, it seems we have
> it as good as it could be with the current approach.
I am benchmarking a patch and just remembered one thing: cset will only
enable the shield if run as root, but it will still run the program
outside otherwise.

Is the benchmark being run as root? if not that might explain the large
variations from run to run.

Cheers,
Rafael

Hi Rafael,

Thanks for mentioning this.

It should be running as root, but I'll double check anyway.

Thanks

Galina

On Mon, Mar 26, 2018 at 10:47 AM, Rafael Avila de Espindola <
rafael.espindola at gmail.com> wrote:
> Galina Kistanova <gkistanova at gmail.com> writes:
>
> > Disabling swap and having a single CPU in the shield group didn't
change
> > much, besides cpu-migrations and context-switches, which now are 0
> > obviously.
> > That clustering remains the same. It is also stable to the number of
runs
> > (I have changed the test to run 20 times in the middle of that range
on
> the
> > right).
> >
> > http://lnt.llvm.org/db_default/v4/link/graph?
> highlight_run=426&plot.9=1.9.6
> >
> > Unless somebody has a good idea what else we should try, it seems we
have
> > it as good as it could be with the current approach.
>
> I am benchmarking a patch and just remembered one thing: cset will only
> enable the shield if run as root, but it will still run the program
> outside otherwise.
>
> Is the benchmark being run as root? if not that might explain the large
> variations from run to run.
>
> Cheers,
> Rafael
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20180326/2c04c9e2/attachment.html>