Re: [gentoo-user] Re: FYI - 2.6.38 desktop responsiveness patch + how to do it now

[Florian Philipp]

Am 19.11.2010 16:36, schrieb Alan McKinnon:
> Apparently, though unproven, at 17:18 on Friday 19 November 2010, Nikos
> Chantziaras did opine thusly:
>
>> On 11/19/2010 04:37 AM, Adam Carter wrote:
>>> 2.6.38 should contain a ~200 line patch that makes a huge difference to
>>> desktop responsiveness under load;
>>> "Tests done by Mike show the maximum latency dropping by over ten times
>>> and the average latency of the desktop by about 60 times"
>>> Ref:
>>> http://www.phoronix.com/scan.php?page=article&item=linux_2637_video&num=1
>>> <http://www.phoronix.com/scan.php?page=article&item=linux_2637_video&num
>>> =1>
>>>
>>> And a RedHat dev reckons you can get the same via configuration;
>>> Ref:
>>> http://www.webupd8.org/2010/11/alternative-to-200-lines-kernel-patch.html
>>>
>>> I havent tried it yet...
>>
>> Doesn't this patch group tasks by TTY?
>
> As I understand it, the kernel patch does group by TTY. Personally I think
> that's just one way of doing it and there could be others. So it's more proof-
> of-concept than TheOneTrueWay(tm)
>
[...]
>
> What *I* would like to see is flash goes into it's own group and gets
> throttled. Everything else running under KDE is in a different group and left
> to run full speed
>

Please help me understand what this patch/script actually does. As far
as I understand it, it groups processes so that the kernel can schedule
more fairly among them. It therefore helps to prevent one group of
processes from starving all others. Is that correct?

First question: What about heavily multi-threaded applications? Does the
kernel already make a similar grouping of threads-per-process as it does
with processes-per-cgroup? Asked in a different way: Would it have any
effect to put single but heavily multi-threaded process such as Tomcat
or Apache with Worker MPM into its own dedicated cgroup?

Second question: When I run a server with different services, does it
make sense to put all services into different cgroups? For example
PostgreSQL in the first, Apache in a second and Cron (and thereby all
batch jobs) in a third? This should be easy enough to do by editing the
init-scripts.

Thanks in advance!
Florian Philipp