lkml.org 
[lkml]   [2006]   [Oct]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Bandwidth Allocations under CFQ I/O Scheduler
Jens Axboe wrote:
> On Wed, Oct 18 2006, Alan Cox wrote:
>
>>Bandwidth is completely silly in this context, iops/sec is merely
>>hopeless 8)
>
>
> Both need the disk to play nicely, if you get into error handling or
> correction, you get screwed. Bandwidth by itself is meaningless, you
> need latency as well to make sense of it.

When writing an IO scheduler, I decided `time' was a pretty good
metric. That's roughly what we use for CPU scheduling as well (but
use nice levels and adjusted by dynamic priorities instead of a
straight % share).

So you could say you want your database to consume no more than 50%
of disk and have your mp3 player get a minimum of 10%. Of course,
that doesn't say anything about what the time slices are, or what
latencies you can expect (1s out of every 10, or 100ms out of every
1000?).

It is still far from perfect, but at least it accounts for seeks vs
throughput reasonably well, and in a device independent manner.

--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-10-18 14:59    [W:0.186 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site