I found many false positive lagging during iocost test.
Since iocg->vtime will be advanced to (vnow - margins.target)
in hweight_after_donation(), which called throw away excess,
the iocg->done_vtime will also be advanced that much.
period_at_vtime <--period_vtime--> vnow
| |
--------------------------------------------------->
|<--->|
margins.target
|->
vtime, done_vtime
If that iocg has some inflight io when vnow, but its done_vtime
is before period_at_vtime, ioc_timer_fn() will think it has
lagging io, even these io maybe issued just before now.
This patch change the condition to check if vdone is before
(period_at_vtime - margins.target) instead of period_at_vtime.
But there is another problem that this patch doesn't fix.
Since vtime will be advanced, we can't check if vtime is
after (vnow - MAX_LAGGING_PERIODS * period_vtime) to tell
whether this iocg pin lagging for too long.
Maybe we can add lagging_periods in iocg to record how many
periods this iocg pin lagging, but I don't know when to clean it.
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
---
block/blk-iocost.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 33a11ba971ea..42e301b7527b 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2259,7 +2259,7 @@ static void ioc_timer_fn(struct timer_list *timer)
time_after64(vtime, vdone) &&
time_after64(vtime, now.vnow -
MAX_LAGGING_PERIODS * period_vtime) &&
- time_before64(vdone, now.vnow - period_vtime))
+ time_before64(vdone, ioc->period_at_vtime - ioc->margins.target))
nr_lagging++;
/*
--
2.36.1
