Re: [PATCH] staircase scheduler v6.4 for 2.6.7-rc3
From: Peter Williams
Date: Tue Jun 08 2004 - 18:57:48 EST
William Lee Irwin III wrote:
On Wed, Jun 09, 2004 at 09:04:23AM +1000, Peter Williams wrote:
There was no need to add the extra overhead of a flag to indicate that a
task was queued for scheduling. Testing whether run_list is empty
achieves the same thing as reliably as the old array == NULL test did.
Overhead? Doubtful. Also, that requires the use of list_del_init()
Yes, that's true.
while dequeueing, which is not in place now. Please do back the claim
with measurements. It should be easy enough to nop out set_task_queued(),
implement task_queued() via !list_empty(), and clear_task_queued() via
INIT_LIST_HEAD() for a quick performance comparison. But I'd say to
merge it even if there's no difference, as it's more self-contained.
Since the principle use of testing array for NULL or not was to find out
if the task was on a run list it seems silly to have a flag to determine
this. All it does is provide an opportunity for the flag to not
accurately reflect whether the task is really on a list or not.
It caused the number of files touched by the staircase patch to increase
by a factor of five which is another good reason to use the alternative.
Peter
--
Dr Peter Williams pwil3058@xxxxxxxxxxxxxx
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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