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Re: [PATCH] gcc parallel make check


On Tue, Sep 16, 2014 at 11:28 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Tue, Sep 16, 2014 at 11:20:37AM +0200, Richard Biener wrote:
>> > This confuses me, but, no matter.  Isnât 8hrs time data?  :-)
>
> It is, but not time(1) data, just wall clock computed from subtracting
> mtimes of my make check output log and make -j48 bootstrap log.
>
>> >> patch toplevel make -j48 -k check took:
>> >> real    40m21.984s
>> >> user    341m51.675s
>> >> sys     112m46.993s
>> >> and with the patch make -j48 -k check took:
>> >> real    32m22.066s
>> >> user    355m1.788s
>> >> sys     117m5.809s
>> >
>> > These numbers are useful to try and ensure the overhead (scaling factor) is reasonable, thanks.
>>
>> A nice improvement indeed.  The patched result is 15 times faster
>> than the serial unpatched run.  So there is room for improvement
>
> Note, the box used was oldish AMD 16-core, no ht, box, haven't tried it on anything

Ah, I assumed -j48 testing means you have 48 cores.  I usually test
with -j12 on my 6-core HT-enabled box.  A factor 15 scaling for 16
CPUs is of course close to the best we can achieve.

Richard.

> more parallel, also it was normal hard disk, etc.  No idea whether anything
> from this is relevant to that though.
> Some CPU time goes into the expect processes, I can retry the build tonight
> and grab also time(1) info from make -k check to see the user/sys times for
> serial testing.
>
>         Jakub


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