Robert Haas <robertmhaas@gmail.com> writes:
> On Mon, Jan 23, 2012 at 12:12 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> The expensive part of what
>>> we do while holding BufFreelistLock is, I think, iterating through
>>> buffers taking and releasing a spinlock on each one (!).
>> Yeah ... spinlocks that, by definition, will be uncontested.
> What makes you think that they are uncontested?
Ah, never mind. I was thinking that we'd only be touching buffers that
were *on* the freelist, but of course this is incorrect. The real
problem there is that BufFreelistLock is also used to protect the
clock sweep pointer. I think basically we gotta find a way to allow
multiple backends to run clock sweeps concurrently. Or else fix
things so that the freelist never (well, hardly ever) runs dry.
regards, tom lane
