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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 |
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| .. | ||
| linux | ||
| sys | ||
| libnvpair.h | ||
| libuutil_common.h | ||
| libuutil_impl.h | ||
| libuutil.h | ||
| libzfs_core.h | ||
| libzfs_impl.h | ||
| libzfs.h | ||
| Makefile.am | ||
| zfeature_common.h | ||
| zfs_comutil.h | ||
| zfs_deleg.h | ||
| zfs_fletcher.h | ||
| zfs_namecheck.h | ||
| zfs_prop.h | ||
| zpios-ctl.h | ||
| zpios-internal.h | ||