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  1. 30 4月, 2007 4 次提交
    • J
      cfq-iosched: rework the whole round-robin list concept · d9e7620e
      由 Jens Axboe 提交于 
      Drawing on some inspiration from the CFS CPU scheduler design, overhaul
the pending cfq_queue concept list management. Currently CFQ uses a
doubly linked list per priority level for sorting and service uses.
Kill those lists and maintain an rbtree of cfq_queue's, sorted by when
to service them.

This unfortunately means that the ionice levels aren't as strong
anymore, will work on improving those later. We only scale the slice
time now, not the number of times we service. This means that latency
is better (for all priority levels), but that the distinction between
the highest and lower levels aren't as big.

The diffstat speaks for itself.

 cfq-iosched.c |  363 +++++++++++++++++---------------------------------
 1 file changed, 125 insertions(+), 238 deletions(-)
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
      d9e7620e
    • J
      cfq-iosched: minor updates · 1afba045
      由 Jens Axboe 提交于 
      - Move the queue_new flag clear to when the queue is selected
- Only select the non-first queue in cfq_get_best_queue(), if there's
  a substantial difference between the best and first.
- Get rid of ->busy_rr
- Only select a close cooperator, if the current queue is known to take
  a while to "think".
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
      1afba045
    • J
      cfq-iosched: development update · 6d048f53
      由 Jens Axboe 提交于 
      - Implement logic for detecting cooperating processes, so we
  choose the best available queue whenever possible.

- Improve residual slice time accounting.

- Remove dead code: we no longer see async requests coming in on
  sync queues. That part was removed a long time ago. That means
  that we can also remove the difference between cfq_cfqq_sync()
  and cfq_cfqq_class_sync(), they are now indentical. And we can
  kill the on_dispatch array, just make it a counter.

- Allow a process to go into the current list, if it hasn't been
  serviced in this scheduler tick yet.

Possible future improvements including caching the cfqq lookup
in cfq_close_cooperator(), so we don't have to look it up twice.
cfq_get_best_queue() should just use that last decision instead
of doing it again.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
      6d048f53
    • J
      cfq-iosched: improve preemption for cooperating tasks · 1e3335de
      由 Jens Axboe 提交于 
      When testing the syslet async io approach, I discovered that CFQ
sometimes didn't perform as well as expected. cfq_should_preempt()
needs to better check for cooperating tasks, so fix that by allowing
preemption of an equal priority queue if the recently queued request
is as good a candidate for IO as the one we are currently waiting for.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
      1e3335de
  3. 28 4月, 2007 36 次提交