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SubjectRe: [PATCH 1/2 v2.0]sched: Removing unused fields from /proc/schedstat
Hi Satoru,

>> I think we can remove rq->sched_switch and rq->sched_switch
>> without no problem because they are meaningless. The former
>> is for old O(1) scheduler and means the number of runqueue
>> switching among active/expired queue. The latter is for
>> SD_WAKE_BALANCE flag and its logic is already gone.
>> However sbe_* are for SD_BALANCE_EXEC flag and sbf_* are for
>> SD_BALANCE_FORK flag. Since both logic for them are still alive,
>> the absence of these accounting is regression in my perspective.
>> In addition, these fields would be useful for analyzing load
>> balance behavior.

The sbe_* & sbf_* counters were added by the commit
68767a0ae428801649d510d9a65bb71feed44dd1 But it was subsequently
removed by the commit 476d139c218e44e045e4bc6d4cc02b010b343939

[ciju@ciju kernel]$ git describe 68767a0ae428801649d510d9a65bb71feed44dd1 --contains
[ciju@ciju kernel]$ git describe 476d139c218e44e045e4bc6d4cc02b010b343939 --contains

So.. it was introduced and removed in 2.6.13 time frame

When the counters were removed the sbe_* sbf_* variable
declarations were not removed. Hence it caused a little confusion.
So I believe these stats were not available and hence can't be
considered as regression.

476d139c218e44e045e4bc6d4cc02b010b343939 consolidated the fork and
exec balance. Thereafter it became non-trivial to provide separate
stats for fork and exec events. So if people think a consolidated
balance-on-event is needed, it can be looked into separately. But
that shouldn't prevent this documentation cleanup patch from
getting in.


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