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cam iosched: Enforce iop limits below the quanta value

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Previously the iops limiter would always allow at least
quanta ios per second as cam_iosched_iops_tick() never set
ios->l_value1 below 1.

Submitted by: Fabian Keil <fk@fabiankeil.de>
Obtained from: ElectroBSD
PR: 221974
This commit is contained in:
Warner Losh 2017-09-22 02:36:32 +00:00
parent cc05c7d256
commit f777123b83
1 changed files with 11 additions and 1 deletions
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12
sys/cam/cam_iosched.c
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@ -415,6 +415,7 @@ cam_iosched_iops_init(struct iop_stats *ios)
ios->l_value1 = ios->current / ios->softc->quanta; ios->l_value1 = ios->current / ios->softc->quanta;
if (ios->l_value1 <= 0) if (ios->l_value1 <= 0)
ios->l_value1 = 1; ios->l_value1 = 1;
ios->l_value2 = 0;
return 0; return 0;
} }
@ -423,9 +424,18 @@ static int
cam_iosched_iops_tick(struct iop_stats *ios) cam_iosched_iops_tick(struct iop_stats *ios)
{ {
if ((ios->softc->total_ticks % ios->softc->quanta) == 0)
ios->l_value2 = 0;
ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16);
if (ios->l_value1 <= 0) /*
* Allow at least one IO per tick until all
* the IOs for this interval have been spent.
*/
if (ios->l_value1 <= 0 && ios->l_value2 < ios->current) {
ios->l_value1 = 1; ios->l_value1 = 1;
ios->l_value2++;
}
return 0; return 0;
} }