Re: [Lsf-pc] [LSF/MM TOPIC][ATTEND] topics I'd like to discuss

Re: [Lsf-pc] [LSF/MM TOPIC][ATTEND] topics I'd like to discuss

[Rik van Riel]

On 02/22/2013 10:35 AM, Larry Woodman wrote:
> 1.) Using mmu notifiers to set up the page tables for integrated
> devices(GPUs) and allowing the generic
>       kernel pagefault handler to resolve translations for those devices.

This functionality is also desired by people who want to run
memory coherency over infiniband and some other very fast
network fabrics, as well as by the people who want to offload
work to specialized cores in their system.

Since there are multiple use cases for this kind of functionality,
I believe that it is important we get the infrastructure right,
and discussing this topic at LSF/MM sounds like a good idea.

> 2.) Replication of pagecache pages on NUMA nodes.

What about this would you like to discuss?

Is there some proposal of code to do this?

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Re: [Lsf-pc] [LSF/MM TOPIC][ATTEND] topics I'd like to discuss

[Larry Woodman]

On 02/22/2013 04:41 PM, Rik van Riel wrote:
> On 02/22/2013 10:35 AM, Larry Woodman wrote:
>> 1.) Using mmu notifiers to set up the page tables for integrated
>> devices(GPUs) and allowing the generic
>>       kernel pagefault handler to resolve translations for those 
>> devices.
>
> This functionality is also desired by people who want to run
> memory coherency over infiniband and some other very fast
> network fabrics, as well as by the people who want to offload
> work to specialized cores in their system.
>
> Since there are multiple use cases for this kind of functionality,
> I believe that it is important we get the infrastructure right,
> and discussing this topic at LSF/MM sounds like a good idea.
Agreed.
>
>> 2.) Replication of pagecache pages on NUMA nodes.
>
> What about this would you like to discuss?
The tradeoffs between local memory access for frequently referenced 
read-only/executable
pages like shared library text and the additional memory consumption 
associated replicating
pages on multiple NUMA nodes.
>
> Is there some proposal of code to do this?
Not yet, I implemented replication of filesystem cache memory on each 
NUMA node
several years ago for a UNIX kernel when NUMA systems first appeared.  
At that
time both memory and caches were much smaller than they are now so the 
tradeoffs
between local memory access and inducing page reclamation were different 
than they
are now.  However there was a significant performance boost on memory 
rich systems
running applications with bloated text sections.

Larry


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Re: [Lsf-pc] [LSF/MM TOPIC][ATTEND] topics I'd like to discuss

[Dave Hansen]

On 02/22/2013 01:41 PM, Rik van Riel wrote:
>> 2.) Replication of pagecache pages on NUMA nodes.
> 
> What about this would you like to discuss?
> 
> Is there some proposal of code to do this?

I did an implementation _long_ ago:

	http://lwn.net/Articles/63512/

Might be fun for someone to glean an idea or two from, although I'm sure
the code has long since bitrotted in to being useless.  It was kinda fun
to read, though. :)

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