Which says that as you ask for pages to put the readahead in, you want to
get a failure back under memory pressure, you push out what you allocated
already and carry on.
>
> > I suspect you really need to go a bit further and get the mapping of
> > all the pages fixed up before you do the actual reads.
>
> Hum, also think about a no-buffer-head deadlock when we're under a
> critical number of buffer heads while having quite a few buffer heads
> locked which are not going to be queued until all needed buffer heads are
> allocated.
All this is probably attempting to be too clever for its own good, there is
probably a much simpler way to get more things happening in parallel. Plus, in
reality, lots of apps will spend some time between read calls processing
data, so there is overlap, a benchmark doing just reads is the end case
of all of this.
Steve
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