Peter Williams wrote:
Paolo Ornati wrote:
On Fri, 20 Jan 2006 08:45:43 +1100
Peter Williams <[email protected]> wrote:
Modifications have been made to spa_ws to (hopefully) address the
issues raised by Paolo Ornati recently and a new entitlement based
interpretation of "nice" scheduler, spa_ebs, which is a cut down
version of the Zaphod schedulers "eb" mode has been added as this
mode of Zaphod performed will for Paolo's problem when he tried it at
my request. Paolo, could you please give these a test drive on your
problem?
---- spa_ws: the problem is still here
(sched_fooler)
./a.out 3000 & ./a.out 4307 &
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5573 paolo 34 0 2396 292 228 R 59.0 0.1 0:24.51 a.out
5572 paolo 34 0 2392 288 228 R 40.7 0.1 0:16.94 a.out
5580 paolo 35 0 4948 1468 372 R 0.3 0.3 0:00.04 dd
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5573 paolo 34 0 2396 292 228 R 59.3 0.1 0:59.65 a.out
5572 paolo 33 0 2392 288 228 R 40.3 0.1 0:41.32 a.out
5440 paolo 28 0 86652 21m 15m S 0.3 4.4 0:03.34 konsole
5580 paolo 37 0 4948 1468 372 R 0.3 0.3 0:00.10 dd
(real life - transcode)
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5585 paolo 33 0 115m 18m 2432 S 90.0 3.7 0:38.04 transcode
5599 paolo 37 0 50996 4472 1872 R 9.1 0.9 0:04.03 tcdecode
5610 paolo 37 0 4948 1468 372 R 0.6 0.3 0:00.19 dd
DD test takes ages in both cases.
What exactly have you done to spa_ws?
I added a "nice aware" version of the throughput bonuses from spa_svr
and renamed them fairness bonus. They don't appear to be working :-(
34 is the priority value that ordinary tasks should end up with i.e. if
they don't look like interactive tasks or CPU hogs. If they look like
interactive tasks they should get a lower one via the interactive bonus
mechanism and if they look like CPU hogs they should get a higher one
via the same mechanism. In addition to this tasks will get bonuses if
they seem to be being treated unfairly i.e. spending too much time on
run queues waiting for CPU access.
Looking at your numbers the transcode task has the priority that I'd
expect it to have but tcdecode and dd seem to have had their priorities
adjusted in the wrong direction. It's almost like they'd been
(incorrectly, obviously) identified as CPU hogs :-(. I'll look into this.
I forgot that I'd also made changes to the "CPU hog" component of the
interactive response as the one I had was useless on heavily loaded
systems. It appears that I made a mistake (I used interactive
sleepiness instead of ordinary sleepiness for detecting CPU hogs) during
these changes which means that tasks that do no interactive sleeping
(such as your dd) get classified as CPU hogs. The transcode task
escapes this because, although its sleeps aren't really interactive,
they're classified as such. More widespread us of TASK_NONINTERACTIVE
would fix this but would need to be done carefully as it would risk
breaking the normal scheduler.
However, in spite of the above, the fairness mechanism should have been
able to generate enough bonus points to get dd's priority back to less
than 34. I'm still investigating why this didn't happen.
Peter
--
Peter Williams [email protected]
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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