Re: Poor PostgreSQL scaling on Linux 2.6.25-rc5 (vs 2.6.22)
- From: Willy Tarreau <w@xxxxxx>
- Date: Mon, 17 Mar 2008 06:21:34 +0100
On Sun, Mar 16, 2008 at 10:16:36PM -0700, Ray Lee wrote:
On Sun, Mar 16, 2008 at 5:44 PM, Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
I don't see how it is really helpful for interactive processes either.
By definition, if they are not CPU bound, then they should be run
quite soon after waking up; if they are CPU bound, then reducing
efficiency by increasing context switches is effectively going to
increase their latency anyway.
How? Are you saying that switching the granularity to, say, 25ms, will
*decrease* the latency of interactive tasks?
And the efficiency we're talking about reducing here is due to the
fact that tasks are hitting cold caches more times per second when the
granularity is smaller, correct? Or are you concerned by another
issue?
Can this be changed by default, please?
Not without benchmarks of interactivity, please. There are far, far
more linux desktops than there are servers. People expect to have to
tune servers (I do, for the servers I maintain). People don't expect
to have to tune a desktop to make it run well.
Oh and even on servers, when your anti-virus proxy reaches a load of 800,
you're happy no to have too large a time-slice so that you regularly get
a chance of being allowed to type in commands over SSH.
Large time-slices are needed only in HPC environments IMHO, where only
one task runs.
Willy
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