Messages in this thread |  | | From | John Alvord <> | Subject | Re: Problem with the O(1) scheduler in 2.4.19 | Date | Tue, 03 Sep 2002 09:46:09 -0700 |
| |
On Tue, 3 Sep 2002 12:28:18 +0200 (CEST), Ingo Molnar <mingo@elte.hu> wrote:
> >On Tue, 3 Sep 2002, Tobias Ringstrom wrote: > >> For the case of a game server, this means that when the CPU utilization >> gets above 50% (roughly), it will switch from -5 to +5 in dynamic >> priority in a few seconds and stay there until the CPU utilization drops >> under 50%. >> >> Is my analysis correct, and is this what we want? > >do you expect a task that uses up 50% CPU time over an extended period of >time to be rated 'interactive'? > >we might make the '50%' rule to be '100% / nr_running_avg', so that if >your task is the only one in the system then it gets rated interactive - >but i suspect it will still be rated a CPU hog if it keeps trying to use >up 50% of CPU time even during busier periods. I have tried the >(1/nr_running) rule in earlier incarnations of the scheduler, and it didnt >make much difference, but we obviously need a boundary case like yours to >see the differences. > >> I tried that yesterday (without the O(1) scheduler), and it does wonders >> for the in-game latency (i.e. ping). I suppose that the dynamic prio >> will still be +5 at 70% CPU utilization even with a HZ of 1000 using the >> O(1) scheduler. Why would it make a difference? > >(it could in theory make a difference in some rare cases, in which the >frequency of sampling resonates with internal timings of the application - >i asked for this only to make sure there are no interactions.) > It seems to me that this condition could arise for any server process which is used by many interactive processes. Imagine 300 users and a server process which needs 70% to do the work. This could be a database server as well as the current game server.
john - 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/
|  |