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  1. 28 Oct, 2009 4 commits
    • Corrado Zoccolo's avatar
      cfq-iosched: enable idling for last queue on priority class · a6d44e98
      Corrado Zoccolo authored 
      cfq can disable idling for queues in various circumstances.
When workloads of different priorities are competing, if the higher
priority queue has idling disabled, lower priority queues may steal
its disk share. For example, in a scenario with an RT process
performing seeky reads vs a BE process performing sequential reads,
on an NCQ enabled hardware, with low_latency unset,
the RT process will dispatch only the few pending requests every full
slice of service for the BE process.

The patch solves this issue by always performing idle on the last
queue at a given priority class > idle. If the same process, or one
that can pre-empt it (so at the same priority or higher), submits a
new request within the idle window, the lower priority queue won't
dispatch, saving the disk bandwidth for higher priority ones.

Note: this doesn't touch the non_rotational + NCQ case (no hardware
to test if this is a benefit in that case).
Signed-off-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      a6d44e98
    • Corrado Zoccolo's avatar
      cfq-iosched: reimplement priorities using different service trees · c0324a02
      Corrado Zoccolo authored 
      We use different service trees for different priority classes.
This allows a simplification in the service tree insertion code, that no
longer has to consider priority while walking the tree.
Signed-off-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      c0324a02
    • Corrado Zoccolo's avatar
      cfq-iosched: preparation to handle multiple service trees · aa6f6a3d
      Corrado Zoccolo authored 
      We embed a pointer to the service tree in each queue, to handle multiple
service trees easily.
Service trees are enriched with a counter.
cfq_add_rq_rb is invoked after putting the rq in the fifo, to ensure
that all fields in rq are properly initialized.
Signed-off-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      aa6f6a3d
    • Corrado Zoccolo's avatar
      cfq-iosched: adapt slice to number of processes doing I/O · 5db5d642
      Corrado Zoccolo authored 
      When the number of processes performing I/O concurrently increases,
a fixed time slice per process will cause large latencies.

This patch, if low_latency mode is enabled,  will scale the time slice
assigned to each process according to a 300ms target latency.

In order to keep fairness among processes:
* The number of active processes is computed using a special form of
running average, that quickly follows sudden increases (to keep latency low),
and decrease slowly (to have fairness in spite of rapid decreases of this
value).

To safeguard sequential bandwidth, we impose a minimum time slice
(computed using 2*cfq_slice_idle as base, adjusted according to priority
and async-ness).
Signed-off-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      5db5d642
  3. 27 Oct, 2009 1 commit
  5. 26 Oct, 2009 4 commits
  7. 13 Oct, 2009 3 commits
  9. 12 Oct, 2009 1 commit
  11. 09 Oct, 2009 3 commits
    • Wu Fengguang's avatar
      writeback: kill space in debugfs item name · 961515f6
      Wu Fengguang authored 
      The space is not script friendly, kill it.
Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      961515f6
    • Wu Fengguang's avatar
      writeback: account IO throttling wait as iowait · d25105e8
      Wu Fengguang authored 
      It makes sense to do IOWAIT when someone is blocked
due to IO throttle, as suggested by Kame and Peter.

There is an old comment for not doing IOWAIT on throttle,
however it has been mismatching the code for a long time.

If we stop accounting IOWAIT for 2.6.32, it could be an
undesirable behavior change. So restore the io_schedule.

CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      d25105e8
    • KOSAKI Motohiro's avatar
      elv_iosched_store(): fix strstrip() misuse · 8c279598
      KOSAKI Motohiro authored 
      elv_iosched_store() ignore the return value of strstrip().  It makes small
inconsistent behavior.

This patch fixes it.

 <before>
 ====================================
 # cd /sys/block/{blockdev}/queue

 case1:
 # echo "anticipatory" > scheduler
 # cat scheduler
 noop [anticipatory] deadline cfq

 case2:
 # echo "anticipatory " > scheduler
 # cat scheduler
 noop [anticipatory] deadline cfq

 case3:
 # echo " anticipatory" > scheduler
 bash: echo: write error: Invalid argument

 <after>
 ====================================
 # cd /sys/block/{blockdev}/queue

 case1:
 # echo "anticipatory" > scheduler
 # cat scheduler
 noop [anticipatory] deadline cfq

 case2:
 # echo "anticipatory " > scheduler
 # cat scheduler
 noop [anticipatory] deadline cfq

 case3:
 # echo " anticipatory" > scheduler
 noop [anticipatory] deadline cfq

Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      8c279598
  13. 08 Oct, 2009 1 commit
  15. 07 Oct, 2009 3 commits
  17. 06 Oct, 2009 5 commits
  19. 05 Oct, 2009 6 commits
  21. 04 Oct, 2009 9 commits
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