Re: remote mysql is too slow
On Wed, Apr 11, 2012 at 07:18:18AM +0100, Bob Proulx wrote:
> Karl E. Jorgensen wrote:
> > Jumping back in (late) in this thread...
> > Bob Proulx wrote:
> > > > # free -m
> > > > total used free shared buffers cached
> > > > Mem: 7986 7913 73 0 224 6133
> > > > -/+ buffers/cache: 1554 6431
> > > > Swap: 3813 0 3813
> > >
> > > Shows 8G of ram. Good. Shows no swap used. Also good. (But not
> > > necessarily bad if some swap is used. So if you see some swap being
> > > used that isn't necessarily a problem.)
> >
> > Mostly good. Yes. But 6133 Mb Cached is not what I would expect - this
> > indicates that the linux kernel is doing the caching - rather than
> > MySQL. And the MySQL cache for this stuff is (almost) always more
> > efficient.
>
> But at some point the daemon is going to need to write a file to disk.
> That data will get cached at that time. Or are you saying that mysql
> is using or should using O_DIRECT and avoid the cache explicitly?
No - although that might help (marginally) too. The point is that
caching of data in MySQL will be more efficient than caching in the
kernel disk cache; less layers and whatnot.
--
Karl E. Jorgensen
IT Operations
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