From: | David Gould <daveg(at)sonic(dot)net> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Anand Ranganathan <arangana(at)adobe(dot)com>, Alex Eulenberg <aeulenbe(at)adobe(dot)com>, Ashokraj M <ashokraj(at)adobe(dot)com>, Hari <hari(at)adobe(dot)com>, Elein Mustain <mustain(at)adobe(dot)com> |
Subject: | Re: Re: bulk_multi_insert infinite loops with large rows and small fill factors |
Date: | 2012-12-14 23:37:33 |
Message-ID: | 20121214153733.5b2bc2d3@jekyl.davidgould.org |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Fri, 14 Dec 2012 15:39:44 -0500
Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Wed, Dec 12, 2012 at 8:29 AM, David Gould <daveg(at)sonic(dot)net> wrote:
> > We lose noticable performance when we raise fill-factor above 10. Even 20 is
> > slower.
>
> Whoa.
Any interest in a fill-factor patch to place exactly one row per page? That
would be the least contended. There are applications where it might help.
> > During busy times these hosts sometimes fall into a stable state
> > with very high cpu use mostly in s_lock() and LWLockAcquire() and I think
> > PinBuffer plus very high system cpu in the scheduler (I don't have the perf
> > trace in front of me so take this with a grain of salt). In this mode they
> > fall from the normal 7000 queries per second to below 3000.
>
> I have seen signs of something similar to this when running pgbench -S
> tests at high concurrency. I've never been able to track down where
I think I may have seen that with pgbench -S too. I did not have time to
investigate more, but out of a sequence of three minute runs I got most
runs at 300k+ qps and but a couple were around 200k qps.
> the problem is happening. My belief is that once a spinlock starts to
> be contended, there's some kind of death spiral that can't be arrested
> until the workload eases up. But I haven't had much luck identifying
> exactly which spinlock is the problem or if it even is just one...
I agree about the death spiral. I think what happens is all the backends
get synchcronized by waiting and they are more likely to contend again.
-dg
--
David Gould 510 282 0869 daveg(at)sonic(dot)net
If simplicity worked, the world would be overrun with insects.
From | Date | Subject | |
---|---|---|---|
Next Message | Kevin Grittner | 2012-12-14 23:41:49 | Re: Parser Cruft in gram.y |
Previous Message | Dimitri Fontaine | 2012-12-14 23:10:03 | Re: Parser Cruft in gram.y |