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Re: MDEV-5081 - Simple performance improvement for MariaDB
thanks for this information, it is really useful.
According to bzr history fast mutex was added back in 2005. I have a few
guesses why it would have been needed:
- probably at that time mutex implementation wasn't as good as it is now
- probably mutex implementation on some specific platform isn't good enough
As for the hardware: I ran my benchmark on Core 2 Duo (from 2006) but with
recent Ubuntu installed. Results were very similar: fast mutex was outsider.
Moreover adaptive mutex does very similar job much better. Still not as good
as normal mutex.
On Thu, Feb 27, 2014 at 09:08:42PM -0800, Davi Arnaut wrote:
> Hi Sergey,
> I looked into fast mutex in the past  and was never able to get a
> straight answer (even from the original developer) on what was the
> intention behind it and how it made things faster as it actually made
> things slower in the past (Bug#38941, others). There is a comment in
> http://bugs.mysql.com/bug.php?id=58766 highlighting one case where I saw a
> small performance improvement, but even that was highly workload/hardware
> dependent (can't recall which workload exactly, might have been sysbench's
> point select or something similar).
> 1. http://dev.mysql.com/worklog/task/?id=4601
> On Wed, Feb 26, 2014 at 10:36 PM, Sergey Vojtovich <svoj@xxxxxxxxxxx> wrote:
> > Hi Sergei,
> > do you know if we ship any binaries with fast mutex
> > (-DMY_PTHREAD_FASTMUTEX)
> > enabled or officially suggest it? What was it's intention and what loads
> > it was
> > supposed to make faster?
> > I'm trying to understand if fastmutex is worth fixing. It looks like
> > duplication
> > of PTHREAD_MUTEX_ADAPTIVE_NP, so we have double spinning when they're
> > enabled.
> > According to my recent benchmarks it shown worst performance.
> > Thanks,
> > Sergey
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