On Sun, May 14, 2006 at 10:21:45PM +0300, Sven Petai wrote: > > int > > chgsbsize(uip, hiwat, to, max) > > struct uidinfo *uip; > > u_int *hiwat; > > u_int to; > > rlim_t max; > > { > > rlim_t new; > > > > UIDINFO_LOCK(uip); > > > > So the next question is how can that be optimized? > > > > Kris > > hi > > on the 8 core machine this lock was the top contended one with rwatsons patch, > with over 8 million failed acquire attempts. > Originally the unp lock had only ~3 million of those, so this explains the > sharp drop with larger number of threads I suppose. > > I feel like I'm missing some very obvious reason, but wouldn't the simplest > workaround be just to return 1 right away if limit is set to infinity, which > is almost always the case since it's the default, and document on the > login.conf manpage that you might take performance hit with this type of > workloads when you set sbsize limits. I tried removing the locking here but did not see a performance change, so I concluded that it's not actually a bottleneck. FYI, I have been working on the locking profiling tools quite a bit lately, and also have started profiling on a 32-thread sun4v system. I hope to have the patches ready to send out soon (they fix a serious design error in mutex profiling that makes some of the profiling stats meaningless, substantially fix performance (20%-25% cost at the moment instead of >80%), and I also have an implementation of spinlock profiling using ktr that seems to be extremely cheap). All of my other large MP systems are offline though, so the only machines I have for profiling right now are a dual p4 xeon and Kip Macy's 32-way T1 :-) > I wonder if I should set up automatic&periodic performance testing > system, that would run all the tests for example once a week, with > latest current and stable, so that it would be easier for developers > to see how changes affect different workloads. > > If you guys think it would be worthwile, what would be the bechmarks > you would like to see in addition to mysql+supersmack ? This kind of thing might be a bit tricky to set up, but it would be well worth it! Kris
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