Re: Would SSI clustering extensions be of interest to kernel community?

[Constantine Gavrilov]

Please see inline...

Aneesh Kumar K.V wrote:

> I am interested in seeing the changes. I am right now working on 
> getting parts of OpenSSI (www.openssi.org)
> changes merged  upstream. Bruce Walker of the OpenSSI project have a 
> design of implementing cluster wide procs. The
> same doc can be found on www.openssi.org website. The paper talks 
> about how to implement cluster wide proccess model
> without requiring home/deputy concept. But yes it require some core 
> kernel changes. But should be Conditionally enabled
> like selinux. So overhead for non cluster users should be nill.

I am personally not interested in making intrusive kernel changes even 
if it yields in true "single-system image". I want very small changes 
(preferrably none).

> Regarding my work you can see the status here
> http://git.openssi.org/~kvaneesh/gitweb.cgi?p=ci-to-linus.git;a=summary
>
> It only gets the ICS changes. That means it introduce a transport 
> independent kernel cluster framework. Right now it supports two 
> interconnect IPV4 and infiniband verbs.

We also have transport abstraction layer and transport plugins for 
TCP/IP, SDP (Infiniband and possibly others), and SCI (Dolphin).

> I am planning on taking the CFS changes. That should bring in 
> clusterwide shared memory too. The way it was done in OpenSSI
> was to hook a new nopage() function for CFS so that when we page 
> fault, we bring the pages from other node.So i am not sure whether
> one need a VM hook for getting clusterwide shared memory. But without 
> seeing the code i am clueless.
Nopage will be called if there is no pte. That means, with just nopage 
you cannot implement RO-RW transition. If you use nopage only, you 
cannot have multiple readers, because you cannot invalidate all other 
readers if one reader goes read-write. Thus nopage allows single reader 
or single writer whle the page fault hook allows multiple readers and 
single writer.

--
----------------------------------------
Constantine Gavrilov
Kernel Developer
Qlusters Software Ltd
1 Azrieli Center, Tel-Aviv
Phone: +972-3-6081977
Fax:   +972-3-6081841
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