Re: Disabling in-memory write cache for x86-64 in Linux II

[Pavel Machek]

Hi!

> > Yes, but then the temp-file is long-lived enough that it *will* hit
> > the disk anyway. So it's only the "create temporary file and pretty
> > much immediately delete it" case that changes behavior (ie compiler
> > assembly files etc).
> > 
> > If the temp-file is for something like burning an ISO image, the
> > burning part is slow enough that the temp-file will hit the disk
> > regardless of when we start writing it.
> 
> The temp-file IO avoidance is an optimization not a guarantee. If a
> user want to avoid IO seriously, he will probably use tmpfs and
> disable swap.

No, sorry, they can't. Assuming ISO image fits in tmpfs would be
cruel.

> So if we have to do some trade-offs in the optimization, I agree that
> we should optimize more towards the "large copies to USB stick" use case.
> 
> The alternative solution, per-bdi dirty thresholds, could eliminate
> the need to do such trade-offs. So it's worth looking at the two
> solutions side by side.

Yes, please.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
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