Re: [PATCH] speed up SATA

Jeff Garzik
2004-03-28T20:02:50Z

Nuno Silva wrote:
> With this kind of control we could have /etc/init.d/io-optimize that
> paused the startup for 10 seconds and tests every device|controller in
> fstab and optimizes according to the .conf file for latency or speed...
> Or a daemon that retrieves statistics and adjusts the policies every
> minute?
>
> Also, everybody says "do it in userland". This is doing (some of) it in
> userland :)

An iotune daemon that sits in userland -- probably mlockall'd into
memory -- would be fun. Like the existing irqbalance daemon that Red
Hat (disc: my employer) ships, "iotuned" could run in the background,
adjusting policies every so often. It would be a good place to put some
of the more high-level "laptop mode" or "high throughput mode" tunables,
so that the user wouldn't have to worry about the minute details of such
things.

Just watch the IO statistics and tweak the queue settings... Gotta make
sure the queue settings don't get tweaked beyond what the hardware can
do, though.

A good iotune daemon would probably have to pay attention to various VM
statistics as well, since the VM is often the one that decides when to
start writing out stuff... such an app could (quite justifiably)
mushroom into a io-and-vmtune daemon.

This is a side issue from the topic of finding a decent in-kernel
default, of course...

Jeff