2022-06-09 08:23:17

by Chengming Zhou

Subject: [PATCH 1/2] blk-iocost: remove the second superfluous current_hweight

The commit ac33e91e2dac ("blk-iocost: implement vtime loss compensation")
add the second current_hweight() in the loop of active iocgs list to
get old_hwi to calculate the vtime loss of the iocg.

Since the hwi can't change and the first current_hweight already get
hwa and hwi, so this second superfluous current_hweight() can be
removed. There should be no functional changes.

Signed-off-by: Chengming Zhou <[email protected]>
---
block/blk-iocost.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 33a11ba971ea..3cda08224d51 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2238,7 +2238,7 @@ static void ioc_timer_fn(struct timer_list *timer)
/* calc usage and see whether some weights need to be moved around */
list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
u64 vdone, vtime, usage_us;
- u32 hw_active, hw_inuse;
+ u32 hwa, old_hwi;

/*
* Collect unused and wind vtime closer to vnow to prevent
@@ -2246,7 +2246,7 @@ static void ioc_timer_fn(struct timer_list *timer)
*/
vdone = atomic64_read(&iocg->done_vtime);
vtime = atomic64_read(&iocg->vtime);
- current_hweight(iocg, &hw_active, &hw_inuse);
+ current_hweight(iocg, &hwa, &old_hwi);

/*
* Latency QoS detection doesn't account for IOs which are
@@ -2271,15 +2271,15 @@ static void ioc_timer_fn(struct timer_list *timer)

/* see whether there's surplus vtime */
WARN_ON_ONCE(!list_empty(&iocg->surplus_list));
- if (hw_inuse < hw_active ||
+ if (old_hwi < hwa ||
(!waitqueue_active(&iocg->waitq) &&
time_before64(vtime, now.vnow - ioc->margins.low))) {
- u32 hwa, old_hwi, hwm, new_hwi, usage;
+ u32 hwm, new_hwi, usage;
u64 usage_dur;

if (vdone != vtime) {
u64 inflight_us = DIV64_U64_ROUND_UP(
- cost_to_abs_cost(vtime - vdone, hw_inuse),
+ cost_to_abs_cost(vtime - vdone, old_hwi),
ioc->vtime_base_rate);

usage_us = max(usage_us, inflight_us);
@@ -2300,7 +2300,6 @@ static void ioc_timer_fn(struct timer_list *timer)
* Already donating or accumulated enough to start.
* Determine the donation amount.
*/
- current_hweight(iocg, &hwa, &old_hwi);
hwm = current_hweight_max(iocg);
new_hwi = hweight_after_donation(iocg, old_hwi, hwm,
usage, &now);
--
2.36.1

2022-06-10 09:07:03

by Andreas Herrmann

Subject: Re: [PATCH 1/2] blk-iocost: remove the second superfluous current_hweight

On Thu, Jun 09, 2022 at 03:34:49PM +0800, Chengming Zhou wrote:
> The commit ac33e91e2dac ("blk-iocost: implement vtime loss compensation")
> add the second current_hweight() in the loop of active iocgs list to
> get old_hwi to calculate the vtime loss of the iocg.
>
> Since the hwi can't change and the first current_hweight already get
> hwa and hwi, so this second superfluous current_hweight() can be
> removed. There should be no functional changes.
>
> Signed-off-by: Chengming Zhou <[email protected]>

FWIW. Looks ok.
Reviewed-by: Andreas Herrmann <[email protected]>