Re: [RFC PATCH] cfq-iosced: Implement IOPS mode and group_idletunable V3

[Vivek Goyal]

On Sat, Jul 24, 2010 at 11:07:07AM +0200, Corrado Zoccolo wrote:
> On Sat, Jul 24, 2010 at 10:51 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> > To me this sounds like slice_idle=0 is the right default then, as it
> > gives useful behaviour for all systems linux runs on.
> No, it will give bad performance on single disks, possibly worse than
> deadline (deadline at least sorts the requests between different
> queues, while CFQ with slice_idle=0 doesn't even do this for readers).

Not sure if CFQ will be worse than deadline with slice_idle=0. CFQ has
some inbuilt things which should help.

- Readers preempt Writers
- All writers go in one single queue (at one prio level), readers get
  their individual queues and can outnumber writers.

So I guess CFQ with slice_idle=0 should not be worse than deadline in terms
of read latencies.

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