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Improve outlier latency by implementing batch size for bioq_disksort
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Authored by imp on Sep 11 2015, 4:19 PM.
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Details

Reviewers
kib
emax
Summary

Implement maximum batch size for the disksort algorithm (also called
max car size in the literature). This limits the number of requests
that are batched together before starting a new batch. It has little
effect on the average service time, but can have a large effect on the
worst service time.

Submitted by: emax@

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rS FreeBSD src repository - subversion
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Buildable 486
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imp retitled this revision from to Improve outlier latency by implementing batch size for bioq_disksort.
imp updated this object.
imp edited the test plan for this revision. (Show Details)
emax added a reviewer: emax.
This revision is now accepted and ready to land.Sep 11 2015, 6:21 PM
kib added a reviewer: kib.

IMO the batch size should be per-queue, but this is probably fine for now.

sys/kern/subr_disk.c
28

I do not like that this knob is under debug OID, is it really debugging facility ?

Also, it makes sense to allow the knob to be managed from the very beginning of the system lifetime, mark it as CTLFAG_RWTUN perhaps.