| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Dave Chinner <david(at)fromorbit(dot)com> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Jim Nasby <jim(at)nasby(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, Mel Gorman <mgorman(at)suse(dot)de>, Josh Berkus <josh(at)agliodbs(dot)com>, Kevin Grittner <kgrittn(at)ymail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Joshua Drake <jd(at)commandprompt(dot)com>, "lsf-pc(at)lists(dot)linux-foundation(dot)org" <lsf-pc(at)lists(dot)linux-foundation(dot)org>, Magnus Hagander <magnus(at)hagander(dot)net> |
| Subject: | Re: [Lsf-pc] Linux kernel impact on PostgreSQL performance |
| Date: | 2014-01-16 00:13:27 |
| Message-ID: | 5928.1389831207@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Dave Chinner <david(at)fromorbit(dot)com> writes:
> On Wed, Jan 15, 2014 at 02:29:40PM -0800, Jeff Janes wrote:
>> And most importantly, "Also, please don't freeze up everything else in the
>> process"
> If you hand writeback off to the kernel, then writeback for memory
> reclaim needs to take precedence over "metered writeback". If we are
> low on memory, then cleaning dirty memory quickly to avoid ongoing
> allocation stalls, failures and potentially OOM conditions is far more
> important than anything else.....
I think you're in violent agreement, actually. Jeff's point is exactly
that we'd rather the checkpoint deadline slid than that the system goes
to hell in a handbasket for lack of I/O cycles. Here "metered" really
means "do it as a low-priority task".
regards, tom lane
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