Fine-grained locking for POSIX local sockets (UNIX domain sockets)

Kris Kennaway kris at
Sun May 7 18:23:15 UTC 2006

On Sun, May 07, 2006 at 07:16:34PM +0100, Robert Watson wrote:
> On Sun, 7 May 2006, Sven Petai wrote:
> >I performed tests on a 4 * dualcore 2Ghz opteron system (so 8 cores in 
> >total).
> >
> >In general with 10 parallel smacker threads the performance seems to go up 
> >with your patch by ~44% and with 100 parallel threads it goes down ~25%
> This is an interesting effect I need to explore.  Kris reported much 
> increased contention on locks within the process (between threads) when 
> running with my patch.  It would be interesting to know what the effect on 
> average query time is -- perhaps it has gone down and we're looking at 
> increased scheduler related contention.
> I noticed the results in the tests seem somewhat variable.  I've noticed 
> that MySQL bennchmarking is heavily affected by test run time and order.  
> It's not atypical when running a series of identical tests to see a first 
> result half the end rate, a second result *better* than the end rate, and 
> then it balance out between the two.  For example, I see the following on a 

Also, I see a slow but statistically significant deterioration in
performance over time.  Maybe mysql's memory is getting fragmented or

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