On Tue, Oct 20, 2009 at 1:05 AM, Michael Widenius <mo...@askmonty.org> wrote: > > Hi! > >>>>>> "MARK" == MARK CALLAGHAN <mdcal...@gmail.com> writes: > > MARK> On Mon, Oct 19, 2009 at 5:52 AM, Sergei Golubchik <ser...@pisem.net> > wrote: >>> Hi, Monty! >>> >>> On Oct 19, Michael Widenius wrote: >>>> >>>> I just finished applying / modifying / rewriting the userstats patch >>>> to MariaDB 5.2 and will commit this in a moment. >>> >>> I wonder if anybody cares to monitor mutex usage in MySQL. >>> >>> This patch adds few new global mutexes that are locked at least once per >>> statement (or more). >>> >>> Without benchmark results one can only speculate whether it will affect >>> users or not. > > MARK> I am willing to bet that Monty's patch makes sysbench readonly much > MARK> slower with high concurrency on an 8-core server. But those problems > MARK> have been fixed in recent versions of the patch. > > One should note that I changed the patch so that there is minimal > overhead (in the order of 4 if) if the userstat is not enabled (ie, > the userstat variable is not set)
I should have run tests first. Fortunately I didn't bet a lot of money. I will do that now (test v4 google patch, maria 5.2, 5.0.37 unmodified, 5.1.38 unmodified with 1.0.4 plugin) and confirm or deny my claim. I measured approximately zero overhead from the SHOW TABLE_STATS feature in the Facebook patch listed below using sysbench readonly on an 8-core server. > > Where can I find that newer version of the patch or can you describe > what changes needs to be done ? For SHOW TABLE_STATS, look at http://bazaar.launchpad.net/~mysqlatfacebook/mysqlatfacebook/trunk/revision/53, and also revisions 55 and 56 For SHOW USER_STATS see the big v4 google patch: http://google-mysql-tools.googlecode.com/svn/trunk/mysql-patches/all.v4-mysql-5.0.37.patch.gz The key to making SHOW TABLE_STATS faster is: * cache pointers into global_table_stats using handler::version_table_stats * updating stats prior to getting LOCK_open when possible (see bzr revision 53 above) * remove code for SHOW INDEX_STATS, doing that efficiently requires more changes than I am willing to maintain -- someone should fund that work The key to making SHOW USER_STATS faster is: * cache pointers into global_user_stats using THD::thd_user_stats_version * get rid of the code that computes concurrent connections per account I want to review your changes to see whether I can reuse your improvements for my code. Both table and user stats would be cleaner were the stats stored in an existing global user or table object. I think such an object exists for user but not for table (the 'shared' table object isn't shared yet). -- Mark Callaghan mdcal...@gmail.com _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : maria-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
