Messages in this thread | | | Date | Tue, 27 Feb 2007 00:41:30 +1100 | From | Nick Piggin <> | Subject | Re: SMP performance degradation with sysbench |
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Nick Piggin wrote: > Rik van Riel wrote: > >> Lorenzo Allegrucci wrote: >> >>> Hi lkml, >>> >>> according to the test below (sysbench) Linux seems to have scalability >>> problems beyond 8 client threads: >>> http://jeffr-tech.livejournal.com/6268.html#cutid1 >>> http://jeffr-tech.livejournal.com/5705.html >>> Hardware is an 8-core amd64 system and jeffr seems willing to try more >>> Linux versions on that machine. >>> Anyway, is there anyone who can reproduce this? >> >> >> >> I have reproduced it on a quad core test system. >> >> With 4 threads (on 4 cores) I get a high throughput, with >> approximately 58% user time and 42% system time. >> >> With 8 threads (on 4 cores) I get way lower throughput, >> with 37% user time, 29% system time 35% idle time! >> >> The maximum time taken per query also increases from >> 0.0096s to 0.5273s. Ouch! >> >> I don't know if this is MySQL, glibc or Linux kernel, >> but something strange is going on... > > > Like you, I'm also seeing idle time start going up as threads increase. > > I initially thought this was a problem with the multiprocessor scheduler, > because the pattern is exactly like some artificat in the load balancing.
"artificat"
Wow. I must need some sleep :) Please excuse any other typos!
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