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SubjectRe: [PATCH v2 5/7] sched: add a new SD_SHARE_POWERDOMAIN for sched_domain
On 19 March 2014 12:05, Preeti U Murthy <preeti@linux.vnet.ibm.com> wrote:
> On 03/19/2014 03:22 PM, Vincent Guittot wrote:
>> On 19 March 2014 07:21, Preeti U Murthy <preeti@linux.vnet.ibm.com> wrote:
>>> Hi Vincent,
>>>
>>> On 03/18/2014 11:26 PM, Vincent Guittot wrote:
>>>> A new flag SD_SHARE_POWERDOMAIN is created to reflect whether groups of CPUs
>>>> in a sched_domain level can or not reach different power state. As an example,
>>>> the flag should be cleared at CPU level if groups of cores can be power gated
>>>> independently. This information can be used to add load balancing level between
>>>> group of CPUs than can power gate independantly. The default behavior of the
>>>> scheduler is to spread tasks across CPUs and groups of CPUs so the flag is set
>>>> into all sched_domains.
>>>
>>> I don't see this flag being set either in sd_init() or in
>>> default_topology[]. Should not the default_topology[] flag setting
>>> routines set this flag at every level of sched domain along with other
>>> topology flags, unless the arch wants to override it?
>>
>> Hi Preeti
>>
>> I have made the choice to not add it in the default table for the
>> moment because the scheduler behavior is not changed. It will be added
>> with patchset that will take advantage of this flag in the load
>> balance decision.
>
> Ok if you are looking at setting this flag in the default topology table
> then [patch 7/7]:sched: powerpc: Add SD_SHARE_POWERDOMAIN for SMT level
> looks good to me. Please add my Reviewed-by to this patch.
>
> However if you are looking at initializing this flag as being set by
> default in sd_init() then the archs will have to revert the flag, rather
> than set it in their respective topology tables for the sched domains
> which have their groups power gated. In which case the [patch 7/7]
> would be incorrect.
> But wait, I see that you mention that the topology level flags are
> left to the archs to set if required. So I am assuming you will not set
> the SD_SHARE_POWER_DOMAIN flag in sd_init() right?

Yes, it will not be set in sd_init but with the function pointer of the table

Vincent

>
> Regards
> Preeti U Murthy
>>
>> Regards,
>> Vincent
>>
>>>
>>> Regards
>>> Preeti U Murthy
>>>> This flag is part of the topology flags that can be set by arch.
>>>>
>>>> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
>>>> ---
>>>> include/linux/sched.h | 1 +
>>>> kernel/sched/core.c | 9 ++++++---
>>>> 2 files changed, 7 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>>>> index 6479de4..7048369 100644
>>>> --- a/include/linux/sched.h
>>>> +++ b/include/linux/sched.h
>>>> @@ -861,6 +861,7 @@ enum cpu_idle_type {
>>>> #define SD_BALANCE_WAKE 0x0010 /* Balance on wakeup */
>>>> #define SD_WAKE_AFFINE 0x0020 /* Wake task to waking CPU */
>>>> #define SD_SHARE_CPUPOWER 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 */
>>>> #define SD_SERIALIZE 0x0400 /* Only a single load balancing instance */
>>>> #define SD_ASYM_PACKING 0x0800 /* Place busy groups earlier in the domain */
>>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>>>> index 0b51ee3..224ec3b 100644
>>>> --- a/kernel/sched/core.c
>>>> +++ b/kernel/sched/core.c
>>>> @@ -5298,7 +5298,8 @@ static int sd_degenerate(struct sched_domain *sd)
>>>> SD_BALANCE_FORK |
>>>> SD_BALANCE_EXEC |
>>>> SD_SHARE_CPUPOWER |
>>>> - SD_SHARE_PKG_RESOURCES)) {
>>>> + SD_SHARE_PKG_RESOURCES |
>>>> + SD_SHARE_POWERDOMAIN)) {
>>>> if (sd->groups != sd->groups->next)
>>>> return 0;
>>>> }
>>>> @@ -5329,7 +5330,8 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
>>>> SD_BALANCE_EXEC |
>>>> SD_SHARE_CPUPOWER |
>>>> SD_SHARE_PKG_RESOURCES |
>>>> - SD_PREFER_SIBLING);
>>>> + SD_PREFER_SIBLING |
>>>> + SD_SHARE_POWERDOMAIN);
>>>> if (nr_node_ids == 1)
>>>> pflags &= ~SD_SERIALIZE;
>>>> }
>>>> @@ -5946,7 +5948,8 @@ static int sched_domains_curr_level;
>>>> (SD_SHARE_CPUPOWER | \
>>>> SD_SHARE_PKG_RESOURCES | \
>>>> SD_NUMA | \
>>>> - SD_ASYM_PACKING)
>>>> + SD_ASYM_PACKING | \
>>>> + SD_SHARE_POWERDOMAIN)
>>>>
>>>> static struct sched_domain *
>>>> sd_init(struct sched_domain_topology_level *tl, int cpu)
>>>>
>>>
>>
>


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