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  1. 02 Mar, 2012 1 commit
  3. 15 Feb, 2012 3 commits
    • Tejun Heo's avatar
      block: exit_io_context() should call elevator_exit_icq_fn() · 621032ad
      Tejun Heo authored 
      While updating locking, b2efa052 "block, cfq: unlink
cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation
from exit_io_context() to the final ioc put.  While this doesn't cause
catastrophic failure, it effectively removes task exit notification to
elevator and cause noticeable IO performance degradation with CFQ.

On task exit, CFQ used to immediately expire the slice if it was being
used by the exiting task as no more IO would be issued by the task;
however, after b2efa052, the notification is lost and disk could sit
idle needlessly, leading to noticeable IO performance degradation for
certain workloads.

This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates
elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it
from exit_io_context().  ICQ_EXITED flag is added to avoid invoking
the callback more than once for the same icq.

Walking icq_list from ioc side and invoking elevator callback requires
reverse double locking.  This may be better implemented using RCU;
unfortunately, using RCU isn't trivial.  e.g. RCU protection would
need to cover request_queue and queue_lock switch on cleanup makes
grabbing queue_lock from RCU unsafe.  Reverse double locking should
do, at least for now.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-and-bisected-by: default avatarShaohua Li <shli@kernel.org>
LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com>
Tested-by: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      621032ad
    • Tejun Heo's avatar
      block: simplify ioc_release_fn() · 2274b029
      Tejun Heo authored 
      Reverse double lock dancing in ioc_release_fn() can be simplified by
just using trylock on the queue_lock and back out from ioc lock on
trylock failure.  Simplify it.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Tested-by: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      2274b029
    • Tejun Heo's avatar
      block: replace icq->changed with icq->flags · d705ae6b
      Tejun Heo authored 
      icq->changed was used for ICQ_*_CHANGED bits.  Rename it to flags and
access it under ioc->lock instead of using atomic bitops.
ioc_get_changed() is added so that the changed part can be fetched and
cleared as before.

icq->flags will be used to carry other flags.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Tested-by: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      d705ae6b
  5. 14 Feb, 2012 34 commits
  7. 13 Feb, 2012 2 commits
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