Date: Sun, 21 Apr 2002 23:53:21 -0700 (PDT) From: Poul-Henning Kamp <phk@FreeBSD.org> To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/kern subr_disklabel.c Message-ID: <200204220653.g3M6rLd11713@freefall.freebsd.org>
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phk 2002/04/21 23:53:21 PDT
Modified files:
sys/kern subr_disklabel.c
Log:
Comment out Kirks io-request priority hack until we can do this in a
civilized way which doesn't cause grief.
The problem is that it is not generally safe to cast a "struct bio
*" to a "struct buf *". Things like ccd, vinum, ata-raid and GEOM
constructs bio's which are not entrails of a struct buf.
Also, curthread may or may not have anything to do with the I/O request
at hand.
The correct solution can either be to tag struct bio's with a
priority derived from the requesting threads nice and have disksort
act on this field, this wouldn't address the "silly-seek syndrome"
where two equal processes bang the diskheads from one edge to the
other of the disk repeatedly.
Alternatively, and probably better: a sleep should be introduced
either at the time the I/O is requested or at the time it is completed
where we can be sure to sleep in the right thread.
The sleep also needs to be in constant timeunits, 1/hz can be practicaly
any sub-second size, at high HZ the current code practically doesn't
do anything.
Revision Changes Path
1.65 +5 -0 src/sys/kern/subr_disklabel.c
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