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  1. 14 Apr, 2009 1 commit
    • Gautham R Shenoy's avatar
      sched: Nominate idle load balancer from a semi-idle package. · f711f609
      Gautham R Shenoy authored 
      Currently the nomination of idle-load balancer is done by choosing the first
idle cpu in the nohz.cpu_mask. This may not be power-efficient, since
such an idle cpu could come from a completely idle core/package thereby
preventing the whole core/package from being in a low-power state.

For eg, consider a quad-core dual package system. The cpu numbering need
not be sequential and can something like [0, 2, 4, 6] and [1, 3, 5, 7].
With sched_mc/smt_power_savings and the power-aware IRQ balance, we try to keep
as fewer Packages/Cores active. But the current idle load balancer logic
goes against this by choosing the first_cpu in the nohz.cpu_mask and not
taking the system topology into consideration.

Improve the algorithm to nominate the idle load balancer from a semi idle
cores/packages thereby increasing the probability of the cores/packages being
in deeper sleep states for longer duration.

The algorithm is activated only when sched_mc/smt_power_savings != 0.
Signed-off-by: default avatarGautham R Shenoy <ego@in.ibm.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20090414045530.7645.12175.stgit@sofia.in.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      f711f609
  3. 09 Apr, 2009 2 commits
    • Paul Turner's avatar
      sched: remove redundant hierarchy walk in check_preempt_wakeup · 002f128b
      Paul Turner authored 
      Impact: micro-optimization

Under group scheduling we traverse up until we are at common siblings
to make the wakeup comparison on.

At this point however, they should have the same parent so continuing
to check up the tree is redundant.
Signed-off-by: default avatarPaul Turner <pjt@google.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <alpine.DEB.1.00.0904081520320.30317@kitami.corp.google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      002f128b
    • Nathan Lynch's avatar
      sched: do not count frozen tasks toward load · e3c8ca83
      Nathan Lynch authored 
      Freezing tasks via the cgroup freezer causes the load average to climb
because the freezer's current implementation puts frozen tasks in
uninterruptible sleep (D state).

Some applications which perform job-scheduling functions consult the
load average when making decisions.  If a cgroup is frozen, the load
average does not provide a useful measure of the system's utilization
to such applications.  This is especially inconvenient if the job
scheduler employs the cgroup freezer as a mechanism for preempting low
priority jobs.  Contrast this with using SIGSTOP for the same purpose:
the stopped tasks do not count toward system load.

Change task_contributes_to_load() to return false if the task is
frozen.  This results in /proc/loadavg behavior that better meets
users' expectations.
Signed-off-by: default avatarNathan Lynch <ntl@pobox.com>
Acked-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatarNigel Cunningham <nigel@tuxonice.net>
Tested-by: default avatarNigel Cunningham <nigel@tuxonice.net>
Cc: <stable@kernel.org>
Cc: containers@lists.linux-foundation.org
Cc: linux-pm@lists.linux-foundation.org
Cc: Matt Helsley <matthltc@us.ibm.com>
LKML-Reference: <20090408194512.47a99b95@manatee.lan>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      e3c8ca83
  5. 08 Apr, 2009 2 commits
  7. 07 Apr, 2009 35 commits
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