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SubjectRe: why swap at all?
Date
On Saturday 29 May 2004 01:28, Bernd Eckenfels wrote:
> In article <200405290037.17775.vda@port.imtp.ilyichevsk.odessa.ua> you wrote:
> >> The benchmark involved was ls. It took several seconds. If I ran it
> >> again in 5 seconds or so, it was fine. Much longer and it would take
> >> several seconds again. Sounds like pages getting evicted in LRU order.
> >
> > By what magic system can know that you are going to do ls again
> > in 2 minutes?
>
> The problem is more about the blocks cp touches, less about predicting the
> ls workload.
>
> > cp should use fadvise() and say that it _really_ does not need those
> > pages.
>
> Yes, indeed. On the other hand the sequential read could be detected by the
> kernel, too.

Looks like it was. ls' read was sequential, too, so it did not get any
advantage. If you can definitely show that streaming io
(say, cat hugefile >/dev/null) flushes _non_ sequentially read data
(pages with program/library code, data of e.g. your Mozilla, etc),
please submit a report to lkml. VM gurus said more than once
that they _want_ to fix things, but need to know how to reproduce.
--
vda

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