| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: spin_delay() for ARM |
| Date: | 2020-04-10 20:22:09 |
| Message-ID: | 31850.1586550129@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2020-04-10 13:09:13 +0530, Amit Khandekar wrote:
>> On my Intel Xeon machine with 8 cores, I tried to test PAUSE also
>> using a sample C program (attached spin.c).
> PAUSE doesn't operate on the level of the CPU scheduler. So the OS won't
> just schedule another process - you won't see different CPU usage if you
> measure it purely as the time running. You should be able to see a
> difference if you measure with a profiler that shows you data from the
> CPUs performance monitoring unit.
A more useful test would be to directly experiment with contended
spinlocks. As I recall, we had some test cases laying about when
we were fooling with the spin delay stuff on Intel --- maybe
resurrecting one of those would be useful?
regards, tom lane
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