| 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: | 2005-11-25 04:02:37 |
| Message-ID: | Pine.LNX.4.58.0511242249540.13062@eon.cs |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | 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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