On Fri, 2015-03-27 at 15:25 +0800, Wanpeng Li wrote:
> 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 <sri...@linux.vnet.ibm.com>
> Signed-off-by: Wanpeng Li <wanpeng...@linux.intel.com>
> ---
> kernel/sched/fair.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0576ce0..1d3e17f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7639,7 +7639,8 @@ static void nohz_idle_balance(struct rq *this_rq, enum
> cpu_idle_type idle)
> int balance_cpu;
>
> if (idle != CPU_IDLE ||
> - !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
> + !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)) ||
> + need_resched())
> goto end;
How about having:
if (idle != CPU_IDLE || need_resched() ||
!test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
which wouldn't require adding a new line.
Besides that:
Reviewed-by: Jason Low <jason.l...@hp.com>
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