Re: [PATCH/RFC] Simplified Readahead

[Nick Piggin]

Steven Pratt wrote:
> Andrew Morton wrote:
>
> > Steven Pratt <slpratt@xxxxxxxxxxxxxx> wrote:
> >  
> >
> > > would like to offer up an alternative simplified design which will 
> > > not only make the code easier to maintain,
> > >   
> >
> >
> > We won't know that until all functionality is in place.
> >  
> Ok, but both you and Nick indicated that the queue congestion isn't 
> needed,

I would have thought that always doing the readahead would provide a
more graceful degradation, assuming the readahead algorithm is fairly
accurate, and copes with things like readahead thrashing (which we
hope is the case).

> > I do think we should skip the I/O for POSIX_FADV_WILLNEED against a
> > congested queue.  I can't immediately think of a good reason for skipping
> > the I/O for normal readahead.
> >  

I don't see why you should skip the readahead for FADVISE_WILLNEED
either. Presumably if someone needs this, they really need it. We
should aim for optimal behaviour when the apis are being used correctly...
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