mirror_zfs/module
Richard Yao bc17f1047a Enable Linux read-ahead for a single page on ZVOLs
Linux has read-ahead logic designed to accelerate sequential workloads.
ZFS has its own read-ahead logic called zprefetch that operates on both
ZVOLs and datasets. Having two prefetchers active at the same time can
cause overprefetching, which unnecessarily reduces IOPS performance on
CoW filesystems like ZFS.

Testing shows that entirely disabling the Linux prefetch results in
a significant performance penalty for reads while commensurate benefits
are seen in random writes. It appears that read-ahead benefits are
inversely proportional to random write benefits, and so a single page
of Linux-layer read-ahead appears to offer the middle ground for both
workloads.

Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Issue #5902
2017-05-04 18:00:27 -04:00
..
avl Fix uninitialized variable in avl_add() 2016-07-25 14:21:34 -07:00
icp [icp] fpu and asm cleanup for linux 2017-03-07 12:59:31 -08:00
nvpair OpenZFS 7812 - Remove gender specific language 2017-02-24 11:07:04 -08:00
unicode codebase style improvements for OpenZFS 6459 port 2017-01-22 13:25:40 -08:00
zcommon More ashift improvements 2017-05-03 09:31:05 -07:00
zfs Enable Linux read-ahead for a single page on ZVOLs 2017-05-04 18:00:27 -04:00
zpios codebase style improvements for OpenZFS 6459 port 2017-01-22 13:25:40 -08:00
.gitignore module/.gitignore: Add *.dwo (#4580) 2016-05-02 09:07:04 -07:00
Makefile.in GZIP compression offloading with QAT accelerator 2017-03-22 17:58:47 -07:00