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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hi Guarav –<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Yes, if Nitin is correct and you set up virtio correctly, using
virtio for tmem should work for both lguest and KVM. There is a possibility
that there may be a small performance problem, but just getting it to work would
be very interesting.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><br>
Thanks,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Dan<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Gaurav Kukreja
[mailto:mailme.gaurav@gmail.com] <br>
<b>Sent:</b> Tuesday, February 09, 2010 11:27 AM<br>
<b>To:</b> Nitin Gupta<br>
<b>Cc:</b> rusty@rustcorp.com.au; tmem-devel@oss.oracle.com<br>
<b>Subject:</b> Re: [Tmem-devel] Implementing Transcendent Memory on Lguest<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span class=apple-style-span><span style='font-size:10.0pt;
font-family:"Arial","sans-serif"'>While I am trying to figure out, all what you
people are saying, :-p.<o:p></o:p></span></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>I
would like to know, if it would be beneficial, in anyway, to take this
direction. As for my project, I am looking forward to implementation in lguest,
but I would like to extend the project to KVM too.<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>On Tue, Feb 9, 2010 at 8:58 PM, Dan Magenheimer <<a
href="mailto:dan.magenheimer@oracle.com">dan.magenheimer@oracle.com</a>>
wrote:<o:p></o:p></p>
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<p class=MsoNormal>> From: Nitin Gupta [mailto:<a
href="mailto:ngupta@vflare.org">ngupta@vflare.org</a>]<br>
><o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'>> On Tue, Feb 9, 2010 at
4:49 AM, Dan Magenheimer<br>
> <<a href="mailto:dan.magenheimer@oracle.com">dan.magenheimer@oracle.com</a>>
wrote:<br>
> >> However, I could not understand your coherence issue: this vswap<br>
> >> driver simply sends swap page to hypervisor synchronously.<br>
> ><br>
> > I am asking if anything in the virtio "layer" buffers<br>
> > the data, making it appear to the client that the data<br>
> > has been copied from/to the hypervisor (and all of tmem's<br>
> > data structures updated in the hypervisor) but it really<br>
> > hasn't happened yet. If so, bad things can happen.<br>
> ><br>
><br>
> I think we can set "virtqueue" size to 1 *and* make it work<br>
> synchronously (this is what vswap does). This should avoid<br>
> any buffering problem you are concerned with.<o:p></o:p></p>
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<p class=MsoNormal>Excellent!<o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><br>
> On a side note, I think such simplistic behavior can result<br>
> in poor performance but handling swapping case always<br>
> brings surprises so maybe anything fancier -- multiple queues<br>
> having large sizes, working asynchronously -- may be difficult<br>
> to implement.<o:p></o:p></p>
</div>
<p class=MsoNormal>The tmem implementation in Xen has good concurrency<br>
support, so multiple processors swapping to different<br>
places in the same "swaptype" can proceed concurrently<br>
if this is desired.<br>
<br>
See "Swizzling" in the tmem 2.6.32 patch... up to<br>
16 guest vcpus can be swapping simultaneously to<br>
frontswap.<br>
<br>
So I think for swapping (at least in Linux) there might be more<br>
flexibility for asynchronicity but I don't think that<br>
applies to cleancache.<br>
<span style='color:#888888'><br>
Dan</span><o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><br>
<br clear=all>
<br>
-- <br>
Gaurav Kukreja<br>
<br>
+91 997 030 1257<o:p></o:p></p>
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