On Thu, Jan 21, 2021 at 07:04:50PM +0800, Huaixin Chang wrote:
> In this patch, we introduce the notion of CFS bandwidth burst. Unused
> "quota" from pervious "periods" might be accumulated and used in the
> following "periods". The maximum amount of accumulated bandwidth is
> bounded by "burst". And the maximun amount of CPU a group can consume in
> a given period is "buffer" which is equivalent to "quota" + "burst in
> case that this group has done enough accumulation.
>
> Signed-off-by: Huaixin Chang <[email protected]>
> Signed-off-by: Shanpei Chen <[email protected]>
Not a valid SoB chain.
> ---
> kernel/sched/core.c | 91
> ++++++++++++++++++++++++++++++++++++++++++++--------
> kernel/sched/fair.c | 2 ++
> kernel/sched/sched.h | 2 ++
> 3 files changed, 82 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index e7e453492cff..48d3bad12be2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7895,10 +7895,12 @@ static const u64 max_cfs_runtime = MAX_BW *
> NSEC_PER_USEC;
>
> static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
>
> -static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
> +static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
> + u64 burst)
Non standard indentation.
> {
> int i, ret = 0, runtime_enabled, runtime_was_enabled;
> struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
> + u64 buffer;
>
> if (tg == &root_task_group)
> return -EINVAL;
> @@ -7925,6 +7927,16 @@ static int tg_set_cfs_bandwidth(struct task_group *tg,
> u64 period, u64 quota)
> if (quota != RUNTIME_INF && quota > max_cfs_runtime)
> return -EINVAL;
>
> + /*
> + * Bound burst to defend burst against overflow during bandwidth shift.
> + */
> + if (burst > max_cfs_runtime)
> + return -EINVAL;
> +
> + if (quota == RUNTIME_INF)
> + buffer = RUNTIME_INF;
> + else
> + buffer = min(max_cfs_runtime, quota + burst);
Why do we care about buffer when RUNTIME_INF?
