Zygo Blaxell d4b3836493 extentwalker: don't fetch absurd numbers of extents just to throw them away ...

ExtentWalker doesn't gain significant benefits from caching, and the
extra SEARCH_V2 ioctls were blamed for a 33% kernel CPU overhead by perf.

Reduce the number of extents to 16 in lieu of fixing the caching.

This gives a significant speed boost on CPU-bound workloads compared
to the original 1024--almost 40% faster on a single SSD with a filesystem
consisting of raw VM images mounted with compress=zstd.

This also seems to reduce LOGICAL_INO overhead.  Perhaps SEARCH_V2 and
LOGICAL_INO were trying to lock the same extents, and interfering with
each other?

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

2018-09-26 23:29:56 -04:00

..

crucible

extentwalker: don't fetch absurd numbers of extents just to throw them away

2018-09-26 23:29:56 -04:00