Messages in this thread | | | Date | Mon, 2 Mar 2009 13:25:48 +0100 | From | Jens Axboe <> | Subject | Re: The difference of request dir between AS and Deadline I/O scheduler? |
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On Mon, Mar 02 2009, ???? wrote: > Hi, > > I'm little confused about the defination of request dir in AS and > Deadline I/O scheduler. > In AS, the request dir is defined by wheher it's sync: > > data_dir = rq_is_sync(rq); > > But in Deadline, the requests are grouped by read and write. > > Why is there the difference since AS is an extension of Deadline? > what's the consideration?
Because AS uses the sync vs async distinction to decide whether to anticipate a new request from that process. 'sync' is then reads or sync writes, whereas deadline does not distinguish between sync and async writes.
-- Jens Axboe
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