Marcelo Tosatti wrote:
>
> > ...
> > But so little code is actually using READA at this stage that I didn't
> > bother - I first need to go through those paths and make sure that they
> > are in fact complete, working and useful...
>
> I've done some experiments in the past which have shown that doing this
> will cause us to almost _never_ do readahead on IO intensive workloads,
> which ended up decreasing performance instead increasing it.
Interesting. Thanks.
One _could_ make the first readahead page non-READA, and then
make the rest READA. That way, all block-contiguous requests
will be merged, and any non-contiguous requests will be dropped on
the floor if the request queue is full. Which is probably what
we want to happen anyway.
Of course the alternative is to slot a little bmap() call into
the readhead logic :)
> Please make sure to extensively test the propagation of READA through the
> pagecache when you do so...
Extensivelytest is my middle name.
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This archive was generated by hypermail 2b29 : Fri Nov 30 2001 - 21:00:32 EST