Re: mutex contention for the query cache

[Sergei Golubchik]

Hi!

On Jul 03, MARK CALLAGHAN wrote:
> 
> The hot spots are:
> 1) global mutex on query cache
> 2) global mutex on MyISAM key cache
> 3) global mutex on InnoDB memory allocator
> 4) inefficient rw-mutex in InnoDB
> 5) contention on transaction log mutex in InnoDB
... 
> I would like to see SMP performance as the #1 priority for MySQL. It
> may be now, but the fix is to give us new stuff (Maria, Falcon) rather
> than to fix the old stuff.

It's surely more of a priority than it was before.
For example, I keep it in mind all the time as I code (whether it helps
is yet to be seen :)

As for the new vs. old stuff - we cannot fix key cache in 5.0, these
scalability problems often require quite a bit of redesign to be fixed.
Meaning, the fix cannot go in 5.0 or 5.1, we're talking about 6.x at the
earliest. And query cache we will need to fix someday, as it's here to
stay (at least for a while). MyISAM key cache is less of an issue, it is
possible that Maria will replace MyISAM completely (it can work in
MyISAM-compatible non-transactional mode).
 
Regards / Mit vielen Grüssen,
Sergei

-- 
   __  ___     ___ ____  __
  /  |/  /_ __/ __/ __ \/ /   Sergei Golubchik <serg@stripped>
 / /|_/ / // /\ \/ /_/ / /__  Principal Software Engineer/Server Architect
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