> The XFS read path is really the general linux read path, so the
> readahead logic is the same for both. Take a look in mm/filemap.c
> looks for MAX_READAHEAD - it is 31 pages, or 124K bytes, you could
> probably change the algorithm and bump the maximum in here - however,
> readahead just queues I/O to the block layer, the block layer has
> its own maximum sizes for individual I/O requests. You may find
> upping the readahead limit just pushes the problem down the stack
> so to speak.
ok. the MAX_READAHEAD is 'int vm_max_readahead = 31' in 2.2.16. I guess
this is the same as '/proc/sys/vm/max-readahead' (and equally for min-).
What do you think I can do to make Linux make LARGE I/O requests, or at
least serialize them so I can reduce the seeks?
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA
Computers are like air conditioners.
They stop working when you open Windows.