Messages in this thread | | | Date | Wed, 30 Sep 2009 19:09:24 +0400 | From | Pavel Emelyanov <> | Subject | Re: [RFC v2 PATCH 0/8] CFS Hard limits - v2 |
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Srivatsa Vaddagiri wrote: > On Wed, Sep 30, 2009 at 07:55:37PM +0530, Bharata B Rao wrote: >> On Wed, Sep 30, 2009 at 05:36:29PM +0400, Pavel Emelyanov wrote: >>> Bharata B Rao wrote: >>>> Hi, >>>> >>>> Here is the v2 post of hard limits feature for CFS group scheduler. This >>>> RFC post mainly adds runtime borrowing feature and has a new locking scheme >>>> to protect CFS runtime related fields. >>>> >>>> It would be nice to have some comments on this set! >>> I have a question I'd like to ask before diving into the code. >>> Consider I'm a user, that has a 4CPUs box 2GHz each and I'd like >>> to create a container with 2CPUs 1GHz each. Can I achieve this >>> after your patches? >> I am not sure if I understand the GHz specification you mention here. >> Are you saying that you want run a container with 2 CPUS with each of >> them running at half their (frequency)capacity ? >> >> This hard limits scheme is about time based rate limiting where you can >> specify a runtime(=hard limit) and a period for the container and the >> container will not be allowed to consume more than the specified CPU time >> within a given period. > > IMO Pavel's requirement can be met with a hard limit of 25% > > 2 CPU of 1GHz = (1/2 x 4) (1/2 x 2) GHz CPUs > = 1/4 x 4 2GHz CPU > = 25% of (4 2GHz CPU) > > IOW by hard-limiting a container thread to run just 0.5sec every sec on a 2GHz > cpu, it is effectively making progress at the rate of 1GHz?
4CPUS 25% each is not the same as 2CPUS 50% each. OTOH making 2CPU container and setting 50% for both would work, but please look at the problem from the end user point of view. He wants to set 50% of the CPU power. Which setup is better 0.5/1, 1/2 or 0.25/0.5?
If you look at how tc works it proposes the user to select bandwidth in human readable values like kbps or mbps.
> - vatsa >
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