Bug#461630: use CONFIG_FAIR_CGROUP_SCHED instead of CONFIG_FAIR_USER_SCHED

[Frank S. Thomas]

clone 461630 -1
reassign -1 linux-image-2.6.24-1-686
retitle -1 use CONFIG_FAIR_CGROUP_SCHED instead of CONFIG_FAIR_USER_SCHED
tags -1 = 
submitter -1 !
stop

Hello,

linux-image-2.6.24-1-686 is built with the Completely Fair Scheduler 
(CONFIG_FAIR_GROUP_SCHED) and it uses userid as basis for grouping tasks 
(CONFIG_FAIR_USER_SCHED), and therefore provides equal CPU bandwidth to each 
user. This configuration has a severe impact on e.g. a desktop system where a 
CPU intensive program with niceness 19 runs under a user that is not the user 
who uses the desktop. The CPU intensive task gets nearly half of the CPU 
cycles which results in a sluggish desktop. An example of such a program is 
boinc-client (from which this bug has been reassigned).

A possible solution for this issue is to use CONFIG_FAIR_CGROUP_SCHED instead 
of CONFIG_FAIR_USER_SCHED and using cgroups to assign different cpu_shares to 
different tasks. Without any configuration all processes are then in the same 
cgroup and since niceness is retained in the same cgroup this would restore 
the behaviour prior to 2.6.24.

More information regarding this issue can be found here:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/188226
https://bugs.launchpad.net/ubuntu/+source/boinc/+bug/177713

Thanks,
-- 
Frank S. Thomas <fst at debian.org>           PGP public key ID: 0xDC426429
Debian Developer                            finger fst/key at db.debian.org
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