[stgt] [PATCH] add timerfd work scheduler support

FUJITA Tomonori fujita.tomonori at lab.ntt.co.jp
Fri Jan 21 06:55:37 CET 2011

On Thu, 20 Jan 2011 16:12:51 +0200
Alexander Nezhinsky <nezhinsky at gmail.com> wrote:

> > There are 3 different sources of inaccuracy.
> > The first one is related to the random distribution of add_work() calls
> > within the 250 (or whatever) msec timer interval. The second one is related
> > to the random distribution of work expiration times within the 250 msec
> > timer interval. These are bounded by 250 ms, averaging in 125 msec each.
> > ...
> > In your patch the big inaccuracies are doubled and no alleviation as above
> > is provided.
> This means that if you use 500ms then the inaccuracy may be up to
> 1sec, averaging in 500ms.
> When the user asks timeouts in seconds resolution, the acceptable
> accuracy should be
> sub-second, say, maximum half-a-second, shouldn't it?
> For example when 2 sec is requested but actually it may get anywhere
> between 1s and 3s.
> Using 250 msec gets 0.5s inaccuracy bound, which would be acceptable.

I think that it depends on what users want. But the primary user of
this feature is iser (I don't think that isns cares about several
seconds delay). So if you send a patch to decrease the interval to
250ms, I'll apply it.

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