Re: SMP performance degradation with sysbench

[Nick Piggin]

Anton Blanchard wrote:
>  
> Hi Nick,
>
>
> > Anyway, I'll keep experimenting. If anyone from MySQL wants to help look
> > at this, send me a mail (eg. especially with the sched_setscheduler issue,
> > you might be able to do something better).
>
>
> I took a look at this today and figured Id document it:
>
> http://ozlabs.org/~anton/linux/sysbench/
>
> Bottom line: it looks like issues in the glibc malloc library, replacing
> it with the google malloc library fixes the negative scaling:
>
> # apt-get install libgoogle-perftools0
> # LD_PRELOAD=/usr/lib/libtcmalloc.so /usr/sbin/mysqld

Hi Anton,

Very cool. Yeah I had come to the conclusion that it wasn't a kernel
issue, and basically was afraid to look into userspace ;)

That bogus setscheduler thing must surely have never worked, though.
I wonder if FreeBSD avoids the scalability issue because it is using
SCHED_RR there, or because it has a decent threaded malloc implementation.

--
SUSE Labs, Novell Inc.
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