Re: slow startup due to LWLockAssign() spinlock

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: slow startup due to LWLockAssign() spinlock
Date: 2014-04-24 21:28:14
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On 2014-04-24 12:43:13 -0400, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > On 2014-04-24 11:02:44 -0400, Tom Lane wrote:
> >> FWIW, I like the LWLockAssignBatch idea a lot better than the currently
> >> proposed patch. LWLockAssign is a low-level function that has no business
> >> making risky assumptions about the context it's invoked in.
> > I don't think LWLockAssignBatch() is that easy without introducing
> > layering violations. It can't just return a pointer out of the main
> > lwlock array that then can be ++ed clientside because MainLWLockArray's
> > stride isn't sizeof(LWLock).
> Meh. I knew this business of using pointers instead of indexes would
> have some downsides.
> We could return the array stride ... kinda ugly, but since there's
> probably only one consumer for this API, it's not *that* bad. Could
> wrap the stride-increment in a macro, perhaps.

I think I am just going to wait for 9.5 where I sure hope we can
allocate the buffer lwlocks outside the main array...


Andres Freund

Andres Freund
PostgreSQL Development, 24x7 Support, Training & Services

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