Messages in this thread | | | Date | Mon, 26 Jul 2010 10:30:23 -0400 | From | Vivek Goyal <> | Subject | Re: [RFC PATCH] cfq-iosced: Implement IOPS mode and group_idle tunable V3 |
| |
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@infradead.org> 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).
> Setting slice_idle to 0 should be considered only when a single > sequential reader cannot saturate the disk bandwidth, and this happens > only on smart enough hardware with large number of spindles.
I was thinking of writting a user space utility which can launch increasing number of parallel direct/buffered reads from device and if device can sustain more than 1 parallel reads with increasing throughput, then it probably is good indicator that one might be better off with slice_idle=0.
Will try that today...
Vivek
| |