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Re: gprof SELECT COUNT(*) results
- From: Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>
- To: Greg Stark <gsstark(at)mit(dot)edu>
- Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
- Subject: Re: gprof SELECT COUNT(*) results
- Date: Thu, 24 Nov 2005 23:02:37 -0500 (EST)
- Message-id: <Pine(dot)LNX(dot)4(dot)58(dot)0511242249540(dot)13062(at)eon(dot)cs>
On Thu, 24 Nov 2005, Greg Stark wrote: > > > You executed LWLock 2.6 million times in just under 300ms. If my math is right > that's about 115 nanoseconds per lock or about 300 cycles on a 2.6Ghz > processor. > > That sounds like a lot but it's about the right order of magnitude. Was this > on a multiprocessor machine? In which case a big part of that time is probably > spent synchronizing between the processors. > Your math is right iff my math is right :-) It is a 2.4G desktop computer. I may need to write some separate tests to see if this is what we should pay for bus lock instruction. Regards, Qingqing
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