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fixed typos in zfs_per_txg_dirty_frees_percent and added method to observe txg commit interval

Richard Elling 2019-05-08 18:09:24 -07:00
parent 403140dc6c
commit e879b80c68
1 changed files with 4 additions and 3 deletions
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7
ZFS-on-Linux-Module-Parameters.md

@ -2716,9 +2716,10 @@ does not throttle other, perhaps more important, writes.
A side effect of this throttle can impact `zfs receive` workloads that contain a
large number of frees and the [ignore_hole_birth](#ignore_hole_birth) optimization is
disabled. The symptom is that the receive workload causes an increase
in the frequency of txg commits when. Since txg commits also flush data from volatile
caches in HDDs to media, HDD performance can be negatively impacted. Also, since
the frees do not consume much bandwith over the pipe, the pipe can appear to stall.
in the frequency of txg commits. The frequency of txg commits is observable via the
`otime` column of `/proc/spl/kstat/zfs/POOLNAME/txgs`. Since txg commits also flush data
from volatile caches in HDDs to media, HDD performance can be negatively impacted.
Also, since the frees do not consume much bandwidth over the pipe, the pipe can appear to stall.
Thus the overall progress of receives is slower than expected.
A value of zero will disable this throttle.