Messages in this thread | | | Date | Fri, 2 Oct 2009 18:22:40 +0200 | From | Ingo Molnar <> | Subject | Re: IO scheduler based IO controller V10 |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Fri, 2 Oct 2009, Jens Axboe wrote: > > > > It's really not that simple, if we go and do easy latency bits, then > > throughput drops 30% or more. > > Well, if we're talking 500-950% improvement vs 30% deprovement, I > think it's pretty clear, though. Even the server people do care about > latencies. > > Often they care quite a bit, in fact.
The other thing is that latency is basically a given property in any system - as an app writer you have to live with it, there's not much you can do to improve it.
Bandwidth on the other hand is a lot more engineerable, as it tends to be about batching things and you can batch in user-space too. Batching is often easier to do than getting good latencies.
Then there's also the fact that the range of apps that care about bandwidth is a lot smaller than the range of apps which care about latencies. The default should help more apps - i.e. latencies.
Ingo
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