Comments on: I/O schedulers seriously revisited

By: Peter Zaitsev

Peter Zaitsev — Sat, 31 Jan 2009 06:55:14 +0000

One interesting thing to note – the schedules keep their names but they are constantly tuned. The behavior I observed for “as” vs “deadline” few years ago (well before cfq was born) is not the same as it is now.

By: Domas Mituzas

Domas Mituzas — Sat, 31 Jan 2009 00:44:23 +0000

William, ‘just’ ;-)

By: William Newton

William Newton — Fri, 30 Jan 2009 21:12:02 +0000

“The worst part is that Deadline is enabled by default just on community distributions, like Ubuntu Server (though Ubuntu desktop kernel has CFQ by default).”

What? From your test results it looks like deadline is much better. If its the default on servers, thats a good thing. I think. Please elaberate on what you meant.

By: Domas Mituzas

Domas Mituzas — Mon, 26 May 2008 20:02:42 +0000

Nat,
there were only writes – reads generally are served from buffer pool.
There were no other I/O requests.

ionice doesn’t help that much – as it is scheduler dependent, and also – it is just one process.

BTW, the box is 4-core, not 8-core.

By: Nat

Nat — Sun, 23 Mar 2008 15:15:13 +0000

> I created a very simple table and started spamming rows

Did you only write or were there a few reads?
Were there other I/O requests (non submitted by Mysql)?
Did you use ‘ionice’ (Debian: ‘schedutils’ package) in order to set the MySQL process in an appropriate (favored!) I/O scheduling class?
Example: “ionice -c2 -n0 /usr/bin/mysqld_safe …”
(the “realtime” class seems not very efficient, see my website)

By: john allspaw

john allspaw — Mon, 11 Feb 2008 21:11:10 +0000

IIRC, only some newer kernels allow for on-the-fly IO scheduler changes.

We also have our squids set with deadline as well as our DBs.

By: Domas Mituzas

Domas Mituzas — Wed, 06 Feb 2008 07:52:53 +0000

pardon my lingo, innodb-flush-log-at-trx-commit :)

By: Xing

Xing — Wed, 06 Feb 2008 04:42:21 +0000

What is flush=0? Where is this set?

By: Partha Dutta

Partha Dutta — Tue, 05 Feb 2008 23:39:02 +0000

Very curious about the flush=0 flag. Is this a boot parameter or an option for the deadline scheduler?

Thanks, Partha