lkml.org 
[lkml]   [2006]   [May]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC 2/5] sched: Add CPU rate soft caps
Peter Williams wrote:
> Balbir Singh wrote:
>> On 5/26/06, Peter Williams <pwil3058@bigpond.net.au> wrote:
>> <snip>
>>>
>>> Notes:
>>>
>>> 1. To minimize the overhead incurred when testing to skip caps
>>> processing for
>>> uncapped tasks a new flag PF_HAS_CAP has been added to flags.
>>>
>>> 2. The implementation involves the addition of two priority slots to the
>>> run queue priority arrays and this means that MAX_PRIO no longer
>>> represents the scheduling priority of the idle process and can't be
>>> used to
>>> test whether priority values are in the valid range. To alleviate this
>>> problem a new function sched_idle_prio() has been provided.
>>
>> I am a little confused by this. Why link the bandwidth expired tasks a
>> cpu (its caps) to a priority slot? Is this a hack to conitnue using
>> the prio_array? why not move such tasks to the expired array?
>
> Because it won't work as after the array switch they may get to run
> before tasks who aren't exceeding their cap (or don't have a cap).

Another important reason for using these slots is that it allows waking
tasks to preempt tasks that have exceeded their cap.

Peter
--
Peter Williams pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-05-28 02:13    [W:0.096 / U:1.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site