On Thu, 16 Jun, at 09:49:32AM, Yuyang Du wrote:
> SD_BALANCE_{FORK|EXEC|WAKE} flags are for select_task_rq() to select a
> CPU to run a new task or a waking task. SD_WAKE_AFFINE is a flag to
> try selecting the waker CPU to run the waking task.
>
> SD_BALANCE_WAKE is not a sched_domain flag, but SD_WAKE_AFFINE is.
> Conceptually, SD_BALANCE_WAKE should be a sched_domain flag just like
> the other two, so we first make SD_BALANCE_WAKE a sched_domain flag.
>
> Moreover, the semantic of SD_WAKE_AFFINE is included in the semantic
> of SD_BALANCE_WAKE. When in wakeup balancing, it is natual to try
> the waker CPU if the waker CPU is allowed, in that sense, we don't
> need a separate flag to specify it, not mentioning that SD_WAKE_AFFINE
> is almost enabled in every sched_domains.
>
> With the above combined, there is no need to have SD_WAKE_AFFINE, so
> we remove and replace it with SD_BALANCE_WAKE. This can be accomplished
> without any functionality change.
>
> Signed-off-by: Yuyang Du <yuyang...@intel.com>
> ---
> include/linux/sched.h | 1 -
> kernel/sched/core.c | 7 +++----
> kernel/sched/deadline.c | 2 +-
> kernel/sched/fair.c | 9 ++++-----
> kernel/sched/rt.c | 2 +-
> 5 files changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index d74e757..0803abd 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1014,7 +1014,6 @@ extern void wake_up_q(struct wake_q_head *head);
> #define SD_BALANCE_EXEC 0x0004 /* Balance on exec */
> #define SD_BALANCE_FORK 0x0008 /* Balance on fork, clone */
> #define SD_BALANCE_WAKE 0x0010 /* Balance on wakeup */
> -#define SD_WAKE_AFFINE 0x0020 /* Wake task to waking CPU */
> #define SD_SHARE_CPUCAPACITY 0x0080 /* Domain members share cpu power */
> #define SD_SHARE_POWERDOMAIN 0x0100 /* Domain members share power domain */
> #define SD_SHARE_PKG_RESOURCES 0x0200 /* Domain members share cpu pkg
> resources */
I'm curious - doesn't this break userspace ABI? These flags are
exported via procfs, so I would have assumed removing or changing the
value of any of these constants would be forbidden.
