Re: Readahead

[Randy.Dunlap]

On Mon, 26 Sep 2005 22:38:21 -0400 (EDT) Alan Stern wrote:

> Can somebody please tell me where the code is that performs optimistic
> readahead when a process does sequential reads on a block device?

There's filesystem readahead in fs/buffer.c (__breadahead()),
although I don't see any actual callers of it.

However, I'm guessing that you are actually thinking about the
anticipatory IO scheduler (as), which is found in
drivers/block/as-iosched.c.
drivers/block/ll_rw_blk.c also does some readahead (READA) work.

> And can someone explain why those readahead calls are allowed to extend 
> beyond the end of the device?

Nope.

---
~Randy
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