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CVS commit: [tls-maxphys] src/sys/ufs/ufs
Module Name: src
Committed By: tls
Date: Sun Oct 14 14:33:32 UTC 2012
src/sys/ufs/ufs [tls-maxphys]: ufs_readwrite.c
In the FFS writebehind code (ufs_readwrite.c:WRITE()), use division
and multiplication instead of shifts, to accomodate devices with
MAXPHYS that is a multiple of the page size, but not a power of 2.
MegaRAID neatly writes out 192k chunks now.
An open question: is is really a good idea to always writebehind
at the largest size supported by the device? Likely not, as this
could have a major impact on I/O fairness. OS X and Solaris both
seem to limit transfers to 128k likely for this reason (the same
problem exists with the readahead code but since it is adaptive,
it will not *always* do huge transfers).
However, simply imposing a smallish limit like 128k here seems
like a bad idea because then we cannot accomodate greedy devices
like RAID, for which you want something like 128k * number of
data components. Hmmmmmm.
To generate a diff of this commit:
cvs rdiff -u -r1.104 -r126.96.36.199 src/sys/ufs/ufs/ufs_readwrite.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
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