| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Kris Kennaway <kris(at)obsecurity(dot)org> |
| Cc: | performance(at)FreeBSD(dot)org, current(at)FreeBSD(dot)org, Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Anyone interested in improving postgresql scaling? |
| Date: | 2007-04-10 19:52:00 |
| Message-ID: | 555.1176234720@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Kris Kennaway <kris(at)obsecurity(dot)org> writes:
> On Tue, Apr 10, 2007 at 02:46:56PM -0400, Tom Lane wrote:
>> Oh, I'm sure the BSD kernel acts as you describe. But Mark's point is
>> that Postgres never has more than one process waiting on any particular
>> SysV semaphore, and so the problem doesn't really affect us.
> To be clear, some behaviour that postgresql does with sysv semaphores
> causes wakeups of many processes at once. i.e. if you have 20
> clients, you will get up to 20 wakeups. I haven't studied the precise
> cause of this, but it is empirically true. This is the scaling
> problem I described, and it's what mux's patch addresses.
[ shrug... ] To the extent that that happens, it's Postgres' own issue,
and no amount of kernel rejiggering will change it. But I certainly
have no objection to a patch that fixes the kernel behavior ...
regards, tom lane
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