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  1. 04 Jan, 2011 1 commit
  3. 19 Dec, 2010 3 commits
    • Paul Turner's avatar
      sched: Fix interactivity bug by charging unaccounted run-time on entity re-weight · 19e5eebb
      Paul Turner authored 
      Mike Galbraith reported poor interactivity[*] when the new shares distribution
code was combined with autogroups.

The root cause turns out to be a mis-ordering of accounting accrued execution
time and shares updates.  Since update_curr() is issued hierarchically,
updating the parent entity weights to reflect child enqueue/dequeue results in
the parent's unaccounted execution time then being accrued (vs vruntime) at the
new weight as opposed to the weight present at accumulation.

While this doesn't have much effect on processes with timeslices that cross a
tick, it is particularly problematic for an interactive process (e.g. Xorg)
which incurs many (tiny) timeslices.  In this scenario almost all updates are
at dequeue which can result in significant fairness perturbation (especially if
it is the only thread, resulting in potential {tg->shares, MIN_SHARES}
transitions).

Correct this by ensuring unaccounted time is accumulated prior to manipulating
an entity's weight.

[*] http://xkcd.com/619/ is perversely Nostradamian here.
Signed-off-by: default avatarPaul Turner <pjt@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20101216031038.159704378@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      19e5eebb
    • Paul Turner's avatar
      sched: Move periodic share updates to entity_tick() · 43365bd7
      Paul Turner authored 
      Long running entities that do not block (dequeue) require periodic updates to
maintain accurate share values.  (Note: group entities with several threads are
quite likely to be non-blocking in many circumstances).

By virtue of being long-running however, we will see entity ticks (otherwise
the required update occurs in dequeue/put and we are done).  Thus we can move
the detection (and associated work) for these updates into the periodic path.

This restores the 'atomicity' of update_curr() with respect to accounting.
Signed-off-by: default avatarPaul Turner <pjt@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101216031038.067028969@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      43365bd7
    • Ingo Molnar's avatar
      Merge commit 'v2.6.37-rc6' into sched/core · ca680888
      Ingo Molnar authored 
      Merge reason: Update to the latest -rc.
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      ca680888
  5. 16 Dec, 2010 2 commits
  7. 15 Dec, 2010 16 commits
  9. 14 Dec, 2010 18 commits
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