Messages in this thread |  | | Date | Tue, 16 Apr 2002 21:33:04 +0200 | From | Jens Axboe <> | Subject | Re: readahead |
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On Tue, Apr 16 2002, Andrew Morton wrote: > Andries.Brouwer@cwi.nl wrote: > > > > ... > > Do these cards not have a request queue? > > > > The kernel views them as SCSI disks. > > So yes, I can do > > > > blockdev --setra 0 /dev/sdc > > > > Unfortunately that does not help in the least. > > Indeed, the only user of the readahead info is > > readahead.c: get_max_readahead() and it does > > > > blk_ra_kbytes = blk_get_readahead(inode->i_dev) / 2; > > if (blk_ra_kbytes < VM_MIN_READAHEAD) > > blk_ra_kbytes = VM_MAX_READAHEAD; > > > > We need to distinguish between undefined, and explicily zero. > > Yup. The below (untested) patch should fix it up. Assuming > that all drivers use blk_init_queue(), and heaven knows if > that's the case. If not, the readahead window will have to be
set it in blk_queue_make_request(), please.
-- Jens Axboe
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