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  1. 17 9月, 2009 2 次提交
    • P
      sched: Add new wakeup preemption mode: WAKEUP_RUNNING · ad4b78bb
      由 Peter Zijlstra 提交于 
      Create a new wakeup preemption mode, preempt towards tasks that run
shorter on avg. It sets next buddy to be sure we actually run the task
we preempted for.

Test results:

 root@twins:~# while :; do :; done &
 [1] 6537
 root@twins:~# while :; do :; done &
 [2] 6538
 root@twins:~# while :; do :; done &
 [3] 6539
 root@twins:~# while :; do :; done &
 [4] 6540

 root@twins:/home/peter# ./latt -c4 sleep 4
 Entries: 48 (clients=4)

 Averages:
 ------------------------------
        Max          4750 usec
        Avg           497 usec
        Stdev         737 usec

 root@twins:/home/peter# echo WAKEUP_RUNNING > /debug/sched_features

 root@twins:/home/peter# ./latt -c4 sleep 4
 Entries: 48 (clients=4)

 Averages:
 ------------------------------
        Max            14 usec
        Avg             5 usec
        Stdev           3 usec

Disabled by default - needs more testing.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NMike Galbraith <efault@gmx.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
LKML-Reference: <new-submission>
      ad4b78bb
    • I
      sched: Fix TASK_WAKING & loadaverage breakage · eb24073b
      由 Ingo Molnar 提交于 
      Fix this:

top - 21:54:00 up  2:59,  1 user,  load average: 432512.33, 426421.74, 417432.74

Which happens because we now set TASK_WAKING before activate_task().

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      eb24073b
  3. 16 9月, 2009 7 次提交
  5. 15 9月, 2009 19 次提交
  7. 11 9月, 2009 3 次提交
    • J
      writeback: add name to backing_dev_info · d993831f
      由 Jens Axboe 提交于 
      This enables us to track who does what and print info. Its main use
is catching dirty inodes on the default_backing_dev_info, so we can
fix that up.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
      d993831f
    • I
      sched: Fix sched::sched_stat_wait tracepoint field · e1f84508
      由 Ingo Molnar 提交于 
      This weird perf trace output:

  cc1-9943  [001]  2802.059479616: sched_stat_wait: task: as:9944 wait: 2801938766276 [ns]

Is caused by setting one component field of the delta to zero
a bit too early. Move it to later.

( Note, this does not affect the NEW_FAIR_SLEEPERS interactivity bug,
  it's just a reporting bug in essence. )
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nikos Chantziaras <realnc@arcor.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <4AA93D34.8040500@arcor.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e1f84508
    • I
      sched: Disable NEW_FAIR_SLEEPERS for now · 3f2aa307
      由 Ingo Molnar 提交于 
      Nikos Chantziaras and Jens Axboe reported that turning off
NEW_FAIR_SLEEPERS improves desktop interactivity visibly.

Nikos described his experiences the following way:

  " With this setting, I can do "nice -n 19 make -j20" and
    still have a very smooth desktop and watch a movie at
    the same time.  Various other annoyances (like the
    "logout/shutdown/restart" dialog of KDE not appearing
    at all until the background fade-out effect has finished)
    are also gone.  So this seems to be the single most
    important setting that vastly improves desktop behavior,
    at least here. "

Jens described it the following way, referring to a 10-seconds
xmodmap scheduling delay he was trying to debug:

  " Then I tried switching NO_NEW_FAIR_SLEEPERS on, and then
    I get:

    Performance counter stats for 'xmodmap .xmodmap-carl':

         9.009137  task-clock-msecs         #      0.447 CPUs
               18  context-switches         #      0.002 M/sec
                1  CPU-migrations           #      0.000 M/sec
              315  page-faults              #      0.035 M/sec

    0.020167093  seconds time elapsed

    Woot! "

So disable it for now. In perf trace output i can see weird
delta timestamps:

  cc1-9943  [001]  2802.059479616: sched_stat_wait: task: as:9944 wait: 2801938766276 [ns]

That nsec field is not supposed to be that large. More digging
is needed - but lets turn it off while the real bug is found.
Reported-by: NNikos Chantziaras <realnc@arcor.de>
Tested-by: NNikos Chantziaras <realnc@arcor.de>
Reported-by: NJens Axboe <jens.axboe@oracle.com>
Tested-by: NJens Axboe <jens.axboe@oracle.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <4AA93D34.8040500@arcor.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3f2aa307
  9. 09 9月, 2009 3 次提交
  11. 08 9月, 2009 3 次提交
    • M
      sched: Ensure that a child can't gain time over it's parent after fork() · b5d9d734
      由 Mike Galbraith 提交于 
      A fork/exec load is usually "pass the baton", so the child
should never be placed behind the parent.  With START_DEBIT we
make room for the new task, but with child_runs_first, that
room comes out of the _parent's_ hide. There's nothing to say
that the parent wasn't ahead of min_vruntime at fork() time,
which means that the "baton carrier", who is essentially the
parent in drag, can gain time and increase scheduling latencies
for waiters.

With NEW_FAIR_SLEEPERS + START_DEBIT + child_runs_first
enabled, we essentially pass the sleeper fairness off to the
child, which is fine, but if we don't base placement on the
parent's updated vruntime, we can end up compounding latency
woes if the child itself then does fork/exec.  The debit
incurred at fork doesn't hurt the parent who is then going to
sleep and maybe exit, but the child who acquires the error
harms all comers.

This improves latencies of make -j<n> kernel build workloads.
Reported-by: NJens Axboe <jens.axboe@oracle.com>
Signed-off-by: NMike Galbraith <efault@gmx.de>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      b5d9d734
    • P
      sched: Deal with low-load in wake_affine() · 71a29aa7
      由 Peter Zijlstra 提交于 
      wake_affine() would always fail under low-load situations where
both prev and this were idle, because adding a single task will
always be a significant imbalance, even if there's nothing
around that could balance it.

Deal with this by allowing imbalance when there's nothing you
can do about it.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      71a29aa7
    • P
      sched: Remove short cut from select_task_rq_fair() · cdd2ab3d
      由 Peter Zijlstra 提交于 
      select_task_rq_fair() incorrectly skips the wake_affine()
logic, remove this.

When prev_cpu == this_cpu, the code jumps straight to the
wake_idle() logic, this doesn't give the wake_affine() logic
the chance to pin the task to this cpu.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      cdd2ab3d
  13. 07 9月, 2009 1 次提交
  15. 05 9月, 2009 2 次提交