2023-08-10 14:23:58

by Lu Jialin

Subject: [PATCH] psi: update psi irqtime when the irq delta is nozero

If update psi irqtime whether the irq delta is zero or not, the performance
will be degradation when update_rq_clock_task works frequently.
Therefore, just update psi irqtime whether the irq delta is nozero.
performace test of times(libmicro):
1) without psi_account_irqtime in update_rq_clock_task
[root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
prc thr usecs/call samples errors cnt/samp
times 1 1 0.45210 188 0 500

2) psi_account_irqtime in update_rq_clock_task
[root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
prc thr usecs/call samples errors cnt/samp
times 1 1 0.49408 196 0 500

3) psi_account_irqtime in update_rq_clock_task when irq delta is nozero
[root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
prc thr usecs/call samples errors cnt/samp
times 1 1 0.45158 195 0 500

Signed-off-by: Lu Jialin <[email protected]>
---
kernel/sched/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c52c2eba7c73..69c4f229d6d1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -722,7 +722,8 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)

rq->prev_irq_time += irq_delta;
delta -= irq_delta;
- psi_account_irqtime(rq->curr, irq_delta);
+ if (irq_delta)
+ psi_account_irqtime(rq->curr, irq_delta);
delayacct_irq(rq->curr, irq_delta);
#endif
#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
--
2.34.1

2023-08-11 07:23:35

by Chengming Zhou

Subject: Re: [PATCH] psi: update psi irqtime when the irq delta is nozero

On 2023/8/10 21:15, Lu Jialin wrote:
> If update psi irqtime whether the irq delta is zero or not, the performance
> will be degradation when update_rq_clock_task works frequently.
> Therefore, just update psi irqtime whether the irq delta is nozero.
> performace test of times(libmicro):
> 1) without psi_account_irqtime in update_rq_clock_task
> [root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
> Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
> prc thr usecs/call samples errors cnt/samp
> times 1 1 0.45210 188 0 500
>
> 2) psi_account_irqtime in update_rq_clock_task
> [root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
> Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
> prc thr usecs/call samples errors cnt/samp
> times 1 1 0.49408 196 0 500
>
> 3) psi_account_irqtime in update_rq_clock_task when irq delta is nozero
> [root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
> Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
> prc thr usecs/call samples errors cnt/samp
> times 1 1 0.45158 195 0 500
>
> Signed-off-by: Lu Jialin <[email protected]>
> ---
> kernel/sched/core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c52c2eba7c73..69c4f229d6d1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -722,7 +722,8 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
>
> rq->prev_irq_time += irq_delta;
> delta -= irq_delta;
> - psi_account_irqtime(rq->curr, irq_delta);
> + if (irq_delta)
> + psi_account_irqtime(rq->curr, irq_delta);
> delayacct_irq(rq->curr, irq_delta);
> #endif
> #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING

LGTM, thanks.

Reviewed-by: Chengming Zhou <[email protected]>

2023-09-29 06:51:46

by Ingo Molnar

Subject: Re: [PATCH] psi: update psi irqtime when the irq delta is nozero

* Lu Jialin <[email protected]> wrote:

> If update psi irqtime whether the irq delta is zero or not, the performance
> will be degradation when update_rq_clock_task works frequently.
> Therefore, just update psi irqtime whether the irq delta is nozero.
> performace test of times(libmicro):
> 1) without psi_account_irqtime in update_rq_clock_task
> [root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
> Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
> prc thr usecs/call samples errors cnt/samp
> times 1 1 0.45210 188 0 500
>
> 2) psi_account_irqtime in update_rq_clock_task
> [root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
> Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
> prc thr usecs/call samples errors cnt/samp
> times 1 1 0.49408 196 0 500
>
> 3) psi_account_irqtime in update_rq_clock_task when irq delta is nozero
> [root@arm64_perf]# ./times -E -C 200 -L -S -W -N "times" -I 200
> Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
> prc thr usecs/call samples errors cnt/samp
> times 1 1 0.45158 195 0 500
>
> Signed-off-by: Lu Jialin <[email protected]>
> ---
> kernel/sched/core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c52c2eba7c73..69c4f229d6d1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -722,7 +722,8 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
>
> rq->prev_irq_time += irq_delta;
> delta -= irq_delta;
> - psi_account_irqtime(rq->curr, irq_delta);
> + if (irq_delta)
> + psi_account_irqtime(rq->curr, irq_delta);
> delayacct_irq(rq->curr, irq_delta);

Erm, if irq_delta is zero, then a whole bunch of code around the place you
modified becomes NOP as well, right?

Thanks,

Ingo