[Lustre-devel] read ahead

Nikita Danilov Nikita.Danilov at Sun.COM
Tue Dec 11 21:53:59 PST 2007

Andreas Dilger writes:


 > Two areas where our readahead is lacking are:
 > - strided reads (may turn the above 16 x 4kB reads into a situation
 >   where the client will prefetch pages instead of "random" IO, depending
 >   on access pattern, and will avoid prefetch of data the client is not
 >   expecting to use)
 > - limiting the readahead to the rate that the client is actually consuming
 >   it (currently once we detect sequential reads the readahead window grows
 >   eventually to the maximum even if this is far more than what the client
 >   needs)

I wonder how useful can inter-file read-ahead be. For example, starting
an executable almost always incurs a sequence of reads of the shared
libraries, compilation re-reads header files in the same order over and
over again, etc.

 > Cheers, Andreas


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