blk-iocost: calculate iocg->usages[] from iocg->local_stat.usage_us

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Currently, iocg->usages[] which are used to guide inuse adjustments are
calculated from vtime deltas. This, however, assumes that the hierarchical
inuse weight at the time of calculation held for the entire period, which
often isn't true and can lead to significant errors.

Now that we have absolute usage information collected, we can derive
iocg->usages[] from iocg->local_stat.usage_us so that inuse adjustment
decisions are made based on actual absolute usage. The calculated usage is
clamped between 1 and WEIGHT_ONE and WEIGHT_ONE is also used to signal
saturation regardless of the current hierarchical inuse weight.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Tejun Heo 2020-09-01 14:52:44 -04:00 • committed by Jens Axboe

parent 97eb19751f

commit 1aa50d020c

2 changed files with 47 additions and 32 deletions

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70

block/blk-iocost.c

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7

include/trace/events/iocost.h

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