netdev - RE: [RFC] non-preemptible kernel socket for RAMster

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Message-ID: <D3F292ADF945FB49B35E96C94C2061B91257D6FD@nsmail.netscout.com>
Date:	Tue, 5 Jul 2011 13:52:17 -0400
From:	"Loke, Chetan" <Chetan.Loke@...scout.com>
To:	"Dan Magenheimer" <dan.magenheimer@...cle.com>,
	<netdev@...r.kernel.org>
Cc:	"Konrad Wilk" <konrad.wilk@...cle.com>,
	"linux-mm" <linux-mm@...ck.org>
Subject: RE: [RFC] non-preemptible kernel socket for RAMster

> -----Original Message-----
> From: Dan Magenheimer [mailto:dan.magenheimer@...cle.com]
> Sent: July 05, 2011 1:25 PM
> To: Loke, Chetan; netdev@...r.kernel.org
> Cc: Konrad Wilk; linux-mm
> Subject: RE: [RFC] non-preemptible kernel socket for RAMster
> 
> > From: Loke, Chetan [mailto:Chetan.Loke@...scout.com]
> > Sent: Tuesday, July 05, 2011 10:37 AM
> > To: Dan Magenheimer; netdev@...r.kernel.org
> > Cc: Konrad Wilk; linux-mm
> > Subject: RE: [RFC] non-preemptible kernel socket for RAMster
> >
> > > In working on a kernel project called RAMster* (where RAM on a
> > > remote system may be used for clean page cache pages and for swap
> > > pages), I found I have need for a kernel socket to be used when
> >
> > How is RAMster+swap different than NBD's (pending etc?)support for
> SWAP
> > over NBD?
> 
> Hi Chetan --
> 
> Thanks for your question.
> 
> I may be ignorant of details about NBD, but did some quick
> research using google.  If I understand correctly, swap over
> NBD is still writing to a configured swap disk on the remote

Hi - I thought NBD-server needs a backing store(a file). 
Now the file itself could reside on a RAM-drive or disk-drive etc.
And so a remote NBD(disk or RAM) can be mounted locally as a swap
device.
The local client should still see it as a block device.

I haven't used the RAM-drive feature myself but you may want to check if
it
works or even borrow that logic in your code.


> machine.  RAMster is swapping to *RAM* on the remote machine.
> The idea is that most machines are very overprovisioned in
> RAM, and are rarely using all of their RAM, especially when
> a machine is (mostly) idle.  In other words, the "max of
> the sums" of RAM usage on a group of machines is much lower
> than the "sum of the max" of RAM usage.
> 
> So if the network is sufficiently faster than disk for
> moving a page of data, RAMster provides a significant
> performance improvement.  OR RAMster may allow a significant
> reduction in the total amount of RAM across a data center.
> 
> The version of RAMster I am working on now is really
> a proof-of-concept that works over sockets, using the
> ocfs2 cluster layer.  One can easily envision a future
> "exo-fabric" which allows one machine to write to the
> RAM of another machine... for this future hardware,
> RAMster becomes much more interesting.
> 

Or you can also try scst-in-RAM mode(if you want to experiment with
different fabrics).


> Thanks,
> Dan

Thanks
Chetan Loke
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