Re: [pgsql-hackers-win32] Help with tuning this query (with
"Dave Held" <[email protected]>
| Newsgroups | gmane.comp.db.postgresql.performance,gmane.comp.db.postgresql.devel.win32 |
|---|---|
| Message-ID | <[email protected]> |
> -----Original Message----- > From: Tom Lane [mailto:[email protected]] > Sent: Monday, March 07, 2005 4:57 PM > To: John A Meinel > Cc: Dave Held; [email protected]; > [email protected] > Subject: Re: [pgsql-hackers-win32] [PERFORM] Help with tuning > this query > (with > > John A Meinel <[email protected]> writes: > > Dave Held wrote: > >> There is always clock(). > > > My experience with clock() on win32 is that CLOCKS_PER_SEC > > was 1000, and it had a resolution of 55clocks / s. Which is why I suggested QueryPerformanceCounter for Win32. I only suggested clock() for *nix. > The other problem is it measures process CPU time, not elapsed time > which is probably more significant for our purposes. Actually, the bigger problem is that a quick test of clock() on Linux shows that it only has a maximum resolution of 10ms on my hardware. Looks like gettimeofday() is the best choice. > Which brings up a question: just what does QueryPerformanceCounter > measure? I think it measures raw CPU cycles, roughly, which seems like it would more or less correspond to wall time. __ David B. Held Software Engineer/Array Services Group 200 14th Ave. East, Sartell, MN 56377 320.534.3637 320.253.7800 800.752.8129 ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq