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  1. 03 8月, 2015 3 次提交
    • Y
      sched/fair: Provide runnable_load_avg back to cfs_rq · 13962234
      由 Yuyang Du 提交于 
      The cfs_rq's load_avg is composed of runnable_load_avg and blocked_load_avg.
Before this series, sometimes the runnable_load_avg is used, and sometimes
the load_avg is used. Completely replacing all uses of runnable_load_avg
with load_avg may be too big a leap, i.e., the blocked_load_avg is concerned
to result in overrated load. Therefore, we get runnable_load_avg back.

The new cfs_rq's runnable_load_avg is improved to be updated with all of the
runnable sched_eneities at the same time, so the one sched_entity updated and
the others stale problem is solved.
Signed-off-by: NYuyang Du <yuyang.du@intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arjan@linux.intel.com
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: fengguang.wu@intel.com
Cc: len.brown@intel.com
Cc: morten.rasmussen@arm.com
Cc: pjt@google.com
Cc: rafael.j.wysocki@intel.com
Cc: umgwanakikbuti@gmail.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1436918682-4971-7-git-send-email-yuyang.du@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      13962234
    • Y
      sched/fair: Rewrite runnable load and utilization average tracking · 9d89c257
      由 Yuyang Du 提交于 
      The idea of runnable load average (let runnable time contribute to weight)
was proposed by Paul Turner and Ben Segall, and it is still followed by
this rewrite. This rewrite aims to solve the following issues:

1. cfs_rq's load average (namely runnable_load_avg and blocked_load_avg) is
   updated at the granularity of an entity at a time, which results in the
   cfs_rq's load average is stale or partially updated: at any time, only
   one entity is up to date, all other entities are effectively lagging
   behind. This is undesirable.

   To illustrate, if we have n runnable entities in the cfs_rq, as time
   elapses, they certainly become outdated:

     t0: cfs_rq { e1_old, e2_old, ..., en_old }

   and when we update:

     t1: update e1, then we have cfs_rq { e1_new, e2_old, ..., en_old }

     t2: update e2, then we have cfs_rq { e1_old, e2_new, ..., en_old }

     ...

   We solve this by combining all runnable entities' load averages together
   in cfs_rq's avg, and update the cfs_rq's avg as a whole. This is based
   on the fact that if we regard the update as a function, then:

   w * update(e) = update(w * e) and

   update(e1) + update(e2) = update(e1 + e2), then

   w1 * update(e1) + w2 * update(e2) = update(w1 * e1 + w2 * e2)

   therefore, by this rewrite, we have an entirely updated cfs_rq at the
   time we update it:

     t1: update cfs_rq { e1_new, e2_new, ..., en_new }

     t2: update cfs_rq { e1_new, e2_new, ..., en_new }

     ...

2. cfs_rq's load average is different between top rq->cfs_rq and other
   task_group's per CPU cfs_rqs in whether or not blocked_load_average
   contributes to the load.

   The basic idea behind runnable load average (the same for utilization)
   is that the blocked state is taken into account as opposed to only
   accounting for the currently runnable state. Therefore, the average
   should include both the runnable/running and blocked load averages.
   This rewrite does that.

   In addition, we also combine runnable/running and blocked averages
   of all entities into the cfs_rq's average, and update it together at
   once. This is based on the fact that:

     update(runnable) + update(blocked) = update(runnable + blocked)

   This significantly reduces the code as we don't need to separately
   maintain/update runnable/running load and blocked load.

3. How task_group entities' share is calculated is complex and imprecise.

   We reduce the complexity in this rewrite to allow a very simple rule:
   the task_group's load_avg is aggregated from its per CPU cfs_rqs's
   load_avgs. Then group entity's weight is simply proportional to its
   own cfs_rq's load_avg / task_group's load_avg. To illustrate,

   if a task_group has { cfs_rq1, cfs_rq2, ..., cfs_rqn }, then,

   task_group_avg = cfs_rq1_avg + cfs_rq2_avg + ... + cfs_rqn_avg, then

   cfs_rqx's entity's share = cfs_rqx_avg / task_group_avg * task_group's share

To sum up, this rewrite in principle is equivalent to the current one, but
fixes the issues described above. Turns out, it significantly reduces the
code complexity and hence increases clarity and efficiency. In addition,
the new averages are more smooth/continuous (no spurious spikes and valleys)
and updated more consistently and quickly to reflect the load dynamics.

As a result, we have less load tracking overhead, better performance,
and especially better power efficiency due to more balanced load.
Signed-off-by: NYuyang Du <yuyang.du@intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arjan@linux.intel.com
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: fengguang.wu@intel.com
Cc: len.brown@intel.com
Cc: morten.rasmussen@arm.com
Cc: pjt@google.com
Cc: rafael.j.wysocki@intel.com
Cc: umgwanakikbuti@gmail.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1436918682-4971-3-git-send-email-yuyang.du@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      9d89c257
    • Y
      sched/fair: Remove rq's runnable avg · cd126afe
      由 Yuyang Du 提交于 
      The current rq->avg is not used at all since its merge into the kernel,
and the code is in the scheduler's hot path, so remove it.
Tested-by: NDietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: NYuyang Du <yuyang.du@intel.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NDietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arjan@linux.intel.com
Cc: bsegall@google.com
Cc: fengguang.wu@intel.com
Cc: len.brown@intel.com
Cc: morten.rasmussen@arm.com
Cc: pjt@google.com
Cc: rafael.j.wysocki@intel.com
Cc: umgwanakikbuti@gmail.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1436918682-4971-2-git-send-email-yuyang.du@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      cd126afe
  3. 04 7月, 2015 2 次提交
  5. 19 6月, 2015 3 次提交
  7. 23 4月, 2015 1 次提交
  9. 27 3月, 2015 2 次提交
  11. 14 1月, 2015 1 次提交
  13. 04 11月, 2014 2 次提交
  15. 24 9月, 2014 1 次提交
  17. 20 8月, 2014 1 次提交
  19. 16 7月, 2014 1 次提交
  21. 12 2月, 2014 1 次提交
    • T
      cgroup: remove cgroup->name · e61734c5
      由 Tejun Heo 提交于 
      cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection.  Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends.  Replace cgroup->name and all related code with kernfs
name/path constructs.

* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
  of kernfs counterparts, which involves semantic changes.
  pr_cont_cgroup_name() and pr_cont_cgroup_path() added.

* cgroup->name handling dropped from cgroup_rename().

* All users of cgroup_name/path() updated to the new semantics.  Users
  which were formatting the string just to printk them are converted
  to use pr_cont_cgroup_name/path() instead, which simplifies things
  quite a bit.  As cgroup_name() no longer requires RCU read lock
  around it, RCU lockings which were protecting only cgroup_name() are
  removed.

v2: Comment above oom_info_lock updated as suggested by Michal.

v3: dummy_top doesn't have a kn associated and
    pr_cont_cgroup_name/path() ended up calling the matching kernfs
    functions with NULL kn leading to oops.  Test for NULL kn and
    print "/" if so.  This issue was reported by Fengguang Wu.

v4: Rebased on top of 0ab02ca8 ("cgroup: protect modifications to
    cgroup_idr with cgroup_mutex").
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NLi Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      e61734c5
  23. 11 2月, 2014 1 次提交
  25. 28 1月, 2014 1 次提交
  27. 13 1月, 2014 1 次提交
    • P
      sched/clock, x86: Use a static_key for sched_clock_stable · 35af99e6
      由 Peter Zijlstra 提交于 
      In order to avoid the runtime condition and variable load turn
sched_clock_stable into a static_key.

Also provide a shorter implementation of local_clock() and
cpu_clock(int) when sched_clock_stable==1.

                        MAINLINE   PRE       POST

    sched_clock_stable: 1          1         1
    (cold) sched_clock: 329841     221876    215295
    (cold) local_clock: 301773     234692    220773
    (warm) sched_clock: 38375      25602     25659
    (warm) local_clock: 100371     33265     27242
    (warm) rdtsc:       27340      24214     24208
    sched_clock_stable: 0          0         0
    (cold) sched_clock: 382634     235941    237019
    (cold) local_clock: 396890     297017    294819
    (warm) sched_clock: 38194      25233     25609
    (warm) local_clock: 143452     71234     71232
    (warm) rdtsc:       27345      24245     24243
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-eummbdechzz37mwmpags1gjr@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      35af99e6
  29. 17 12月, 2013 1 次提交
  31. 29 10月, 2013 1 次提交
  33. 09 10月, 2013 1 次提交
  35. 13 9月, 2013 1 次提交
  37. 28 6月, 2013 2 次提交
  39. 27 6月, 2013 3 次提交
  41. 22 2月, 2013 1 次提交
  43. 25 1月, 2013 2 次提交
  45. 24 10月, 2012 7 次提交