| From: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, YUriy Zhuravlev <u(dot)zhuravlev(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Move PinBuffer and UnpinBuffer to atomics |
| Date: | 2016-04-06 09:33:02 |
| Message-ID: | CAPpHfds-e0LeMhqxBXsfAvRFs04=GXEp6tYFpc3dON93j=9v2A@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Tue, Apr 5, 2016 at 5:45 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2016-04-05 17:36:49 +0300, Alexander Korotkov wrote:
> > Could the reason be that we're increasing concurrency for LWLock state
> > atomic variable by placing queue spinlock there?
>
> Don't think so, it's the same cache-line either way.
>
Yes, it's very unlikely.
> But I wonder why this could happen during "pgbench -S", because it doesn't
> > seem to have high traffic of exclusive LWLocks.
>
> Yea, that confuses me too. I suspect there's some mis-aligned
> datastructures somewhere. It's hard to investigate such things without
> access to hardware.
>
But it's quite easy to check if it is alignment issue. We can try your
patch but without removing mutex from LWLock struct. If it's alignment
issue, then TPS should become stable again.
(FWIW, I'm working on getting pinunpin committed)
>
Sounds good.
------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Andres Freund | 2016-04-06 09:35:14 | Re: Move PinBuffer and UnpinBuffer to atomics |
| Previous Message | Andres Freund | 2016-04-06 09:28:55 | Re: large regression for parallel COPY |