Messages in this thread | | | Date | Wed, 09 Jun 2004 09:56:23 +1000 | From | Peter Williams <> | Subject | Re: [PATCH] staircase scheduler v6.4 for 2.6.7-rc3 |
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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@bigpond.net.au
"Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce
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