Re: gprof SELECT COUNT(*) results - Mailing list pgsql-hackers

From Qingqing Zhou
Subject Re: gprof SELECT COUNT(*) results
Date
Msg-id Pine.LNX.4.58.0511242249540.13062@eon.cs
Whole thread Raw
In response to Re: gprof SELECT COUNT(*) results  (Greg Stark <gsstark@mit.edu>)
Responses Re: gprof SELECT COUNT(*) results  (Qingqing Zhou <zhouqq@cs.toronto.edu>)
List pgsql-hackers

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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