Messages in this thread | ![/](/images/icornerl.gif) | | Date | Fri, 1 Aug 2003 00:17:31 +0200 (MET DST) | From | Bartlomiej Zolnierkiewicz <> | Subject | Re: Disk performance degradation |
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On Thu, 31 Jul 2003, Andrew Morton wrote:
> mru@users.sourceforge.net (Mĺns Rullgĺrd) wrote: > > > > Mike Dresser <mdresser_l@windsormachine.com> writes: > > > > > Probably for reasons like that. For some reason, I can't set my ICH4 > > > based controller(ASUS P4B533) and Quantum Fireball AS40.0 to more than > > > 255. Kernel is 2.4.21 > > > > It appears that in 2.[56] kernels the unit for readahead is bytes, > > rather than sectors, as used in 2.4 kernels. > > The ioctl which is used by > > blockdev --setra > > is still in 512-byte units. > > There are other backdoors such as IDE-private /proc files which can be used > to set readahead. I'm not sure what units they use, and I don't know what > mechanism hdparm is using to diddle readahead.
in 2.4.x:
/proc/ide/hdX/settings
breada_readahead - BLKRA{GET/SET} file_readahead - BLKFRA{GET/SET}
both are in 1024 bytes units
in 2.6.x they are gone :-).
and hdparm is using BLKRA{GET/SET}
-- Bartlomiej
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