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author | scottl <scottl@FreeBSD.org> | 2013-05-07 08:16:21 +0000 |
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committer | scottl <scottl@FreeBSD.org> | 2013-05-07 08:16:21 +0000 |
commit | a5718800b18e9b041aea3c13a2c790d9da75ed17 (patch) | |
tree | f48f275b48203a9c6a0b01c2f0d6735f550be109 /gnu | |
parent | 7218a7cacea670cef5babb5a6d86ab5afbbce563 (diff) | |
download | FreeBSD-src-a5718800b18e9b041aea3c13a2c790d9da75ed17.zip FreeBSD-src-a5718800b18e9b041aea3c13a2c790d9da75ed17.tar.gz |
Add a sysctl vfs.read_min to complement the exiting vfs.read_max. It
defaults to 1, meaning that it's off.
When read-ahead is enabled on a file, the vfs cluster code deliberately
breaks a read into 2 I/O transactions; one to satisfy the actual read,
and one to perform read-ahead. This makes sense in low-latency
circumstances, but often produces unbalanced i/o transactions that
penalize disks. By setting vfs.read_min, we can tell the algorithm to
fetch a larger transaction that what we asked for, achieving the same
effect as the read-ahead but without the doubled, unbalanced transaction
and the slightly lower latency. This significantly helps our workloads
with video streaming.
Submitted by: emax
Reviewed by: kib
Obtained from: Netflix
Diffstat (limited to 'gnu')
0 files changed, 0 insertions, 0 deletions