Messages in this thread | | | Date | Mon, 26 Jul 2010 10:33:00 -0400 | From | Vivek Goyal <> | Subject | Re: [RFC PATCH] cfq-iosced: Implement IOPS mode and group_idle tunable V3 |
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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).
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
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