On Mon, 09 Jan 2006 16:52:17 +0100
Mike Galbraith <[email protected]> wrote:
> >Care to try an experiment?...
Yes.
With my simple proggy things improve a bit:
./a.out 7000 & ./a.out 6537 &
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5579 paolo 19 0 2392 288 228 R 51.9 0.1 0:22.38 a.out
5578 paolo 20 0 2392 288 228 R 43.9 0.1 0:22.50 a.out
As you can see they don't get priority 15/16 anymore :)
DD test: 256 MB, ~8.5s (instead of 8)
In pratice the more CPU they use the more their priority is penalized...
BUT if I start more of them (3/4) I'm able to fool it.
"./a.out 7000 & ./a.out 6537 & ./a.out 6347 & ./a.out 5873"
2 TOP's snapshots:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5625 paolo 17 0 2392 288 228 R 31.6 0.1 0:10.74 a.out
5626 paolo 17 0 2392 288 228 R 28.8 0.1 0:09.16 a.out
5627 paolo 17 0 2392 288 228 R 22.2 0.1 0:07.59 a.out
5624 paolo 17 0 2392 288 228 R 17.4 0.1 0:08.67 a.out
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5626 paolo 16 0 2392 288 228 R 30.1 0.1 0:39.95 a.out
5627 paolo 16 0 2392 288 228 R 24.1 0.1 0:34.93 a.out
5625 paolo 18 0 2392 288 228 R 23.5 0.1 0:37.53 a.out
5624 paolo 18 0 2392 288 228 R 21.9 0.1 0:37.60 a.out
5193 root 15 0 167m 17m 2916 S 0.2 3.5 0:09.67 X
5638 paolo 18 0 4952 1468 372 R 0.2 0.3 0:00.15 dd
DD test (256MB): real 3m37.122s (instead of 8s)
REAL LIFE TEST (transcode)
While running only transcode it gets priority 25:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5857 paolo 25 0 114m 18m 2424 R 90.9 3.7 0:14.28 transcode
5873 paolo 19 0 49860 4452 1860 S 8.6 0.9 0:01.40 tcdecode
5308 paolo 16 0 86796 22m 15m R 0.2 4.4 0:06.26 konsole
5687 paolo 16 0 98648 37m 9348 S 0.2 7.5 0:02.11 perl
5872 paolo 24 0 21864 1064 600 S 0.2 0.2 0:00.01 tcextract
But if I run also the DD test, "transcode" priority start fluctuating
and can go down to 18/19 (from time to time) interfering with DD:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5694 paolo 19 0 114m 18m 2424 R 75.1 3.7 0:42.29 transcode
5710 paolo 25 0 49856 4452 1860 R 8.0 0.9 0:04.36 tcdecode
5726 paolo 18 0 4952 1468 372 R 4.0 0.3 0:00.77 dd
This seems to happen because also transcode is reading (not directly but
through pipes) from disk so the massive disk usage of DD interferes
with it, this leads to transcode using less CPU and getting better
priority.
The exact behaviour changes time to time... but seems to confirm my
teory.
I don't know how can "nicksched" keep transcode priority always to 40
even when I'm running the DD test... I should retry and see.
PS: yes, transcode is reading from disk, but SLOWLY... i think that a
good read-ahead should fullfill his needs even when doing the HD
stressing DD test, no?
--
Paolo Ornati
Linux 2.6.15-sched_trottle on x86_64
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