linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Steven Sistare <steven.sistare@oracle.com>
To: Valentin Schneider <valentin.schneider@arm.com>,
	mingo@redhat.com, peterz@infradead.org
Cc: subhra.mazumdar@oracle.com, dhaval.giani@oracle.com,
	daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com,
	matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com,
	riel@redhat.com, jbacik@fb.com, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, quentin.perret@arm.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance
Date: Mon, 19 Nov 2018 12:31:34 -0500	[thread overview]
Message-ID: <0d8ceaff-6368-2dff-9e2c-e5928ab39bab@oracle.com> (raw)
In-Reply-To: <9ad62a6f-0269-a5d9-9757-ba5419f9cc1d@arm.com>

On 11/9/2018 2:07 PM, Valentin Schneider wrote:
> Hi Steve,
> 
> On 09/11/2018 12:50, Steve Sistare wrote:
>> Move the update of idle_stamp from idle_balance to the call site in
>> pick_next_task_fair, to prepare for a future patch that adds work to
>> pick_next_task_fair which must be included in the idle_stamp interval.
>> No functional change.
>>
>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>> ---
>>  kernel/sched/fair.c | 23 ++++++++++++++---------
>>  1 file changed, 14 insertions(+), 9 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 9031d39..da368ed 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -3725,6 +3725,8 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
>>  	rq->misfit_task_load = task_h_load(p);
>>  }
>>  
>> +#define IF_SMP(statement)	statement
>> +
> 
> I'm not too hot on those IF_SMP() macros. Since you're not introducing
> any other user for them, what about an inline function for rq->idle_stamp
> setting ? When it's mapped to an empty statement (!CONFIG_SMP) GCC is
> smart enough to remove the rq_clock() that would be passed to it on
> CONFIG_SMP:

That may be true now, but I worry that rq_clock or its subroutines may gain
side effects in the future that prevent the compiler from removing it.  However,
I could push rq_clock into the inline function:

  static inline void rq_idle_stamp_set(rq)    { rq->idle_stamp = rq_clock(rq); }
  static inline void rq_idle_stamp_clear(rq)  { rq->idle_stamp = 0; }

I like that better, do you?

- Steve
 
> ----->8-----
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c11adf3..34d9864 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3725,7 +3725,10 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
>         rq->misfit_task_load = task_h_load(p);
>  }
>  
> -#define IF_SMP(statement)      statement
> +static inline void set_rq_idle_stamp(struct rq *rq, u64 value)
> +{
> +       rq->idle_stamp = value;
> +}
>  
>  static void overload_clear(struct rq *rq)
>  {
> @@ -3772,7 +3775,7 @@ static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
>         return 0;
>  }
>  
> -#define IF_SMP(statement)      /* empty */
> +static inline void set_rq_idle_stamp(struct rq *rq, u64 value) {}
>  
>  static inline void overload_clear(struct rq *rq) {}
>  static inline void overload_set(struct rq *rq) {}
> @@ -6773,12 +6776,12 @@ done: __maybe_unused;
>          * We must set idle_stamp _before_ calling idle_balance(), such that we
>          * measure the duration of idle_balance() as idle time.
>          */
> -       IF_SMP(rq->idle_stamp = rq_clock(rq);)
> +       set_rq_idle_stamp(rq, rq_clock(rq));
>  
>         new_tasks = idle_balance(rq, rf);
>  
>         if (new_tasks)
> -               IF_SMP(rq->idle_stamp = 0;)
> +               set_rq_idle_stamp(rq, 0);
>  
>         /*
>          * Because idle_balance() releases (and re-acquires) rq->lock, it is
> 

  reply	other threads:[~2018-11-19 17:32 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-09 12:50 [PATCH v3 00/10] steal tasks to improve CPU utilization Steve Sistare
2018-11-09 12:50 ` [PATCH v3 01/10] sched: Provide sparsemask, a reduced contention bitmap Steve Sistare
2018-11-27 15:16   ` Steven Sistare
2018-11-28  1:19     ` Omar Sandoval
2018-12-06 16:07       ` Steven Sistare
2018-12-06 18:19         ` Omar Sandoval
2018-11-09 12:50 ` [PATCH v3 02/10] sched/topology: Provide hooks to allocate data shared per LLC Steve Sistare
2018-11-09 12:50 ` [PATCH v3 03/10] sched/topology: Provide cfs_overload_cpus bitmap Steve Sistare
2018-11-09 17:38   ` Valentin Schneider
2018-11-19 17:32     ` Steven Sistare
2018-11-20 12:52       ` Valentin Schneider
2018-11-12 16:42   ` Valentin Schneider
2018-11-19 17:33     ` Steven Sistare
2018-11-20 12:42       ` Valentin Schneider
2018-11-26 19:06         ` Steven Sistare
2018-12-03 16:56           ` Valentin Schneider
2018-12-06 16:40             ` Steven Sistare
2018-12-06 17:28               ` Valentin Schneider
2018-11-09 12:50 ` [PATCH v3 04/10] sched/fair: Dynamically update cfs_overload_cpus Steve Sistare
2018-11-09 12:50 ` [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance Steve Sistare
2018-11-09 19:07   ` Valentin Schneider
2018-11-19 17:31     ` Steven Sistare [this message]
2018-11-20 10:24       ` Valentin Schneider
2018-11-09 12:50 ` [PATCH v3 06/10] sched/fair: Generalize the detach_task interface Steve Sistare
2018-11-09 12:50 ` [PATCH v3 07/10] sched/fair: Provide can_migrate_task_llc Steve Sistare
2018-11-09 12:50 ` [PATCH v3 08/10] sched/fair: Steal work from an overloaded CPU when CPU goes idle Steve Sistare
2018-11-09 12:50 ` [PATCH v3 09/10] sched/fair: disable stealing if too many NUMA nodes Steve Sistare
2018-11-09 12:50 ` [PATCH v3 10/10] sched/fair: Provide idle search schedstats Steve Sistare
2018-11-10 17:08   ` kbuild test robot
2018-11-09 15:02 ` hackbench run scripts Steven Sistare

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=0d8ceaff-6368-2dff-9e2c-e5928ab39bab@oracle.com \
    --to=steven.sistare@oracle.com \
    --cc=daniel.m.jordan@oracle.com \
    --cc=dhaval.giani@oracle.com \
    --cc=jbacik@fb.com \
    --cc=juri.lelli@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=matt@codeblueprint.co.uk \
    --cc=mingo@redhat.com \
    --cc=pavel.tatashin@microsoft.com \
    --cc=peterz@infradead.org \
    --cc=quentin.perret@arm.com \
    --cc=riel@redhat.com \
    --cc=subhra.mazumdar@oracle.com \
    --cc=umgwanakikbuti@gmail.com \
    --cc=valentin.schneider@arm.com \
    --cc=vincent.guittot@linaro.org \
    --subject='Re: [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).