Re: [libvirt] [RFC] Memory controller exploitation in libvirt

24 Aug 2010


      * Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com> [2010-08-24 13:35:10]:
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* Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com> [2010-08-24 11:53:27]:
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Subject: [RFC] Memory controller exploitation in libvirt
Corresponding libvirt public API:
 int virDomainSetMemoryParamters (virDomainPtr domain, 
     				  virMemoryParamterPtr params, 
      		                  unsigned int nparams);
 int virDomainGetMemoryParamters (virDomainPtr domain, 
     				  virMemoryParamterPtr params, 
      		                  unsigned int nparams);
Does nparams imply setting several parameters together? Does bulk
loading help? I would prefer splitting out the API if possible
into
Yes it helps, when parsing the parameters from the domain xml file, we can call
On Tue, 24 Aug 2010 13:05:26 +0530, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
this API and set them at once. BTW, it can also be called with one parameter
if desired.
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virCgroupSetMemory() - already present in src/util/cgroup.c
        virCgroupGetMemory() - already present in src/util/cgroup.c
        virCgroupSetMemorySoftLimit()
        virCgroupSetMemoryHardLimit()
        virCgroupSetMemorySwapHardLimit()
        virCgroupGetStats()
This is at the cgroup level(internal API) and will be implemented in the way
that is suggested. The RFC should not be specific to cgroups. libvirt is
supported on multiple OS and the above described APIs in the RFC are public
API.
I thought we were talking of cgroups in the QEMU driver for Linux.
IMHO the generalization is too big. ESX for example, already abstracts
their WLM/RM needs in their driver.
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SwapHardLimits (memory.memsw_limit_in_bytes) - Maximum swap 
    SwapSoftLimits (Currently not supported by kernel) - Desired swap space
We *dont* support SwapSoftLimits in the memory cgroup controller with
no plans to support it in the future either at this point. The
Ok.
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Tunables memory.limit_in_bytes, memory.softlimit_in_bytes and
    memory.memsw_limit_in_bytes are provided by the memory controller in the
    Linux kernel.
I am not an expert here, so just listing what new elements need to be added
 to the XML schema:
<define name="resource">
    <element memory>
    	<element memoryHardLimit/>
    	<element memorySoftLimit/>
        <element memoryMinGaurantee/>
        <element swapHardLimit/>
        <element swapSoftLimit/>
    </element>
 </define>
I'd prefer a syntax that integrates well with what we currently have
<cgroup>
                <path>...</path>
                <controller>
                <name>..</name>
                <soft limit>...</>
                <hard limit>...</>
                </controller>
        ...
        </cgroup>
Again this is a libvirt domain xml file, IMO, it should not be cgroup specific.
See the comment above. 

-- 
	Three Cheers,
	Balbir