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RE: [Xen-devel] Memory de-duplication (Persistent pages)

This is an interesting idea, but  (1) there is no “standard “ GPU so I don’t think it will be possible to write Xen code generically for this; (2) most of the overhead for searching will be in moving data from RAM to cache... the CPU overhead is probably a small fraction so a GPU may not help much (unless it has a much wider bus to RAM); (3) in tmem’s current deduplication implementation, the search is done synchronously on every put_page... I don’t know if this will work well asynchronously due to locking, existing data structures, etc.



From: Kaustubh Kabra [mailto:kaustubhwise@xxxxxxxxx]
Sent: Wednesday, September 15, 2010 1:09 PM
To: Xen-devel
Cc: Dan Magenheimer
Subject: Re: [Xen-devel] Memory de-duplication (Persistent pages)


To solve memory deduplication in Xen using Gpu :

Current problem :
If Memory deduplication is done on Cpu ,a lot of memory is used for data structures and lot of computation time is wasted in finding duplicate page and becomes waste, if duplicate page is not found.

Proposed GPU solution: Let Gpu perform seraching for a shared page using multiple threads in parallel,improving searching operation and save data structures on GPU device memory ,which is possible. Communication between Cpu and Gpu can be done using inter processor synchronization which is also possible. Cpu process will run as a daemon that will invoke gpu process when ever deduplication is scheduled / if performance is good enough then for every page written in memory.

Correct me , if anything is wrong.

On Mon, Sep 6, 2010 at 11:05 PM, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> wrote:

In my opinion, both could be useful projects.

> -----Original Message-----
> From: Kaustubh Kabra [mailto:kaustubhwise@xxxxxxxxx]
> Sent: Saturday, September 04, 2010 1:02 PM
> To: Xen-devel
> Cc: Dan Magenheimer
> Subject: Re: [Xen-devel] Memory de-duplication (Persistent pages)

> Sir,
> We are pretty clear with the internal working of tmem.
> Now as "ephemeral" pages are already de-duplicated in current
> implementation .
> 1>>So, we propose to do sharing of "persistent" pages also .
> 2>>We also propose n/w bipass manager for "tmem" as its not existing
> currently.
> Will it be really useful ?
> If yes, it will be implemented within stipulated time frame.
> Thank you.

Kaustubh Kabra

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