1. 30 Apr, 2007 9 commits
    • Jens Axboe's avatar
      cfq-iosched: slice offset should take ioprio into account · 67e6b49e
      Jens Axboe authored
      
      
      Use the max_slice-cur_slice as the multipler for the insertion offset.
      Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      67e6b49e
    • Jens Axboe's avatar
      498d3aa2
    • Jens Axboe's avatar
      cfq-iosched: sort IDLE queues into the rbtree · 67060e37
      Jens Axboe authored
      
      
      Same treatment as the RT conversion, just put the sorted idle
      branch at the end of the tree.
      Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      67060e37
    • Jens Axboe's avatar
      cfq-iosched: sort RT queues into the rbtree · 0c534e0a
      Jens Axboe authored
      
      
      Currently CFQ does a linked insert into the current list for RT
      queues. We can just factor the class into the rb insertion,
      and then we don't have to treat RT queues in a special way. It's
      faster, too.
      Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      0c534e0a
    • Jens Axboe's avatar
      [PATCH] cfq-iosched: speed up rbtree handling · cc09e299
      Jens Axboe authored
      
      
      For cases where the rbtree is mainly used for sorting and min retrieval,
      a nice speedup of the rbtree code is to maintain a cache of the leftmost
      node in the tree.
      
      Also spotted in the CFS CPU scheduler code.
      
      Improved by Alan D. Brunelle <Alan.Brunelle@hp.com> by updating the
      leftmost hint in cfq_rb_first() if it isn't set, instead of only
      updating it on insert.
      Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      cc09e299
    • Jens Axboe's avatar
      cfq-iosched: rework the whole round-robin list concept · d9e7620e
      Jens Axboe authored
      
      
      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: default avatarJens Axboe <jens.axboe@oracle.com>
      d9e7620e
    • Jens Axboe's avatar
      cfq-iosched: minor updates · 1afba045
      Jens Axboe authored
      
      
      - 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: default avatarJens Axboe <jens.axboe@oracle.com>
      1afba045
    • Jens Axboe's avatar
      cfq-iosched: development update · 6d048f53
      Jens Axboe authored
      
      
      - 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: default avatarJens Axboe <jens.axboe@oracle.com>
      6d048f53
    • Jens Axboe's avatar
      cfq-iosched: improve preemption for cooperating tasks · 1e3335de
      Jens Axboe authored
      
      
      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: default avatarJens Axboe <jens.axboe@oracle.com>
      1e3335de
  2. 27 Apr, 2007 31 commits