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Re: Userstats patch applied to MariaDB 5.2



>>>>> "MARK" == MARK CALLAGHAN <mdcallag@xxxxxxxxx> writes:

MARK> This includes results from sysbench for Maria 5.2 with/without
MARK> userstat enabled and for several other binaries. The results are
MARK> throughput (transactions per second) for 1, 2, 4, 8, 16, 32 concurrent
MARK> sessions.

MARK> ------------

MARK> This tests many binaries including 5.0.37 with the v2 Google patch (aka 5037v2).
MARK> On a configuration I no longer have access to, 5037v2 had a severe performance
MARK> regression from code in the SHOW [TABLE|USER|_STATISTICS patch. The regression
MARK> was caused by mutex contention. The result on my current platform is
MARK> much less severe,
MARK> but you can see the impact in simple-allcols and simple-handler listed below
MARK> -- compare 5037, 5037v2 and 5037v4.

MARK> I am using glibc 2.5 now and used an older glibc version in the past. I am
MARK> curious if pthread code is that much better on my current platform.

MARK> I thought that the Maria version of that feature would inherit this performance
MARK> problem. Performance loss in Maria is 5% to 10% with userstat enabled for
MARK> high levels of concurrency -- again see results for simple-allcols and
MARK> simple-handle -- and this is much less than the loss in 5037v2, but more
MARK> than the loss in 5037v4 which had fixes for user and table stats code.

Thanks a lot for the numbers!
Shows just that things are as you suspected.

MARK> oltp-ro
MARK>   1         2           4         8         16       32
MARK> concurrent_sessions / binary


MARK> 780     1362    2590    4287    4193    4096    5138pi
MARK> 703     1425    2593    4379    4176    4110    maria.nostat
MARK> 684     1281    2439    4064    3896    3882    maria.stat


MARK> simple-allcols
MARK>   1         2           4           8           16         32
MARK> concurrent_sessions / binary


MARK> 14797   24481   48254   92323   87722   86436   5138pi
MARK> 13418   24980   49777   94425   88083   86854   maria.nostat
MARK> 13062   23378   46636   83449   77714   77245   maria.stat

Do you have any explanation why maria.nostat would be slower than
5138pi ?

I can't think of anything in MariaDB that could cause that kind of
overhead, especially if 5138pi is running with userstats enabled.

Hakan, can you add to your TODO to do a test between MariaDB 5.1 and
MariaDB 5.2 and check if there is any performance degradation with
Mark's test when userstat is not enabled?


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