linux-kernel - RT-Scheduler/cgroups: Possible overuse of resources assigned via cpu.rt_period_us and cpu.rt_runtime

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <485917CF.1010401@uw.no>
Date:	Wed, 18 Jun 2008 16:12:31 +0200
From:	"Daniel K." <dk@...no>
To:	Peter Zijlstra <peterz@...radead.org>, mingo@...e.hu,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RT-Scheduler/cgroups: Possible overuse of resources assigned via
 cpu.rt_period_us and cpu.rt_runtime_us

mkdir /dev/cgroup
mount -t cgroup -o cpu,cpuset cgroup /dev/cgroup

mkdir /dev/cgroup/0

echo 3 > /dev/cgroup/0/cpuset.cpus
echo 0 > /dev/cgroup/0/cpuset.mems
echo 100000 > /dev/cgroup/0/cpu.rt_period_us
echo   5000 > /dev/cgroup/0/cpu.rt_runtime_us

schedtool -R -p 1 -e burnP6 &
[1] 3309
echo 3309 > /dev/cgroup/0/tasks

At this point I'd expect the burnP6 task to use 5% of the available CPU
resources in the cgroup (5000/100000), but the real CPU usage, as
reported by top, is 20% This is 4 times the expected result, and as I
have 4 cores, I think there is a strong hint of correlation there.

Maybe with a 4 core system there really is 4 000 000 us available for
every 1 wall-time second?

However, I have only assigned one core (3) to _this_ cgroup, so I think
this cgroup is overusing its assigned resources.

What do you think?

Daniel K.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/