* [PATCH v2] sched/fair: fix update the nohz.next_balance even if we haven't done any load balance
@ 2015-03-27 7:52 Wanpeng Li
2015-03-27 11:28 ` Srikar Dronamraju
0 siblings, 1 reply; 2+ messages in thread
From: Wanpeng Li @ 2015-03-27 7:52 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra
Cc: Srikar Dronamraju, Jason Low, Preeti U Murthy, linux-kernel, Wanpeng Li
As Srikar pointed out (https://lkml.org/lkml/2015/3/27/26):
| With the current code when the ilb cpus are not free:
| - We would be updating the nohz.next_balance even through we havent done
| any load balance.
| - We might iterate thro the nohz.idle_cpus_mask()s to find balance_cpus.
This patch fix it by adding need_resched check with the idle check, and
keep the need_resched check in for loop to catch ilb get busy.
Suggested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0576ce0..788e42f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7638,7 +7638,7 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
struct rq *rq;
int balance_cpu;
- if (idle != CPU_IDLE ||
+ if (idle != CPU_IDLE || need_resched() ||
!test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
goto end;
--
1.9.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] sched/fair: fix update the nohz.next_balance even if we haven't done any load balance
2015-03-27 7:52 [PATCH v2] sched/fair: fix update the nohz.next_balance even if we haven't done any load balance Wanpeng Li
@ 2015-03-27 11:28 ` Srikar Dronamraju
0 siblings, 0 replies; 2+ messages in thread
From: Srikar Dronamraju @ 2015-03-27 11:28 UTC (permalink / raw)
To: Wanpeng Li
Cc: Ingo Molnar, Peter Zijlstra, Jason Low, Preeti U Murthy, linux-kernel
* Wanpeng Li <wanpeng.li@linux.intel.com> [2015-03-27 15:52:30]:
> As Srikar pointed out (https://lkml.org/lkml/2015/3/27/26):
>
> | With the current code when the ilb cpus are not free:
> | - We would be updating the nohz.next_balance even through we havent done
> | any load balance.
> | - We might iterate thro the nohz.idle_cpus_mask()s to find balance_cpus.
>
> This patch fix it by adding need_resched check with the idle check, and
> keep the need_resched check in for loop to catch ilb get busy.
>
> Suggested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> Reviewed-by: Jason Low <jason.low2@hp.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Looks good to me.
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---
> kernel/sched/fair.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0576ce0..788e42f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7638,7 +7638,7 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
> struct rq *rq;
> int balance_cpu;
>
> - if (idle != CPU_IDLE ||
> + if (idle != CPU_IDLE || need_resched() ||
> !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
> goto end;
>
> --
> 1.9.1
>
--
Thanks and Regards
Srikar Dronamraju
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2015-03-27 7:52 [PATCH v2] sched/fair: fix update the nohz.next_balance even if we haven't done any load balance Wanpeng Li
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