On Thu, 14 Jan 2010, Greg Smith wrote:
Andy Colson wrote:
So if there is very little io, or if there is way way too much, then the
scheduler really doesn't matter. So there is a slim middle ground where
the io is within a small percent of the HD capacity where the scheduler
might make a difference?
That's basically how I see it. There seem to be people who run into
workloads in the middle ground where the scheduler makes a world of
difference. I've never seen one myself, and suspect that some of the reports
of deadline being a big improvement just relate to some buginess in the
default CFQ implementation that I just haven't encountered.
That's the perception I get. CFQ is the default scheduler, but in most
systems I have seen, it performs worse than the other three schedulers,
all of which seem to have identical performance. I would avoid
anticipatory on a RAID array though.
It seems to me that CFQ is simply bandwidth limited by the extra
processing it has to perform.
Matthew
--
Experience is what allows you to recognise a mistake the second time you
make it.
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