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[Xen-devel] Hugepage support to tmem.

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: [Xen-devel] Hugepage support to tmem.
From: ash win <ash_win012006@xxxxxxxxx>
Date: Fri, 22 Oct 2010 04:23:55 +0530 (IST)
Cc: Xen-devel@xxxxxxxxxxxxxxxxxxx, ashwin <vasani.ashwin@xxxxxxxxx>, tmem-devel@xxxxxxxxxxxxxx
Delivery-date: Thu, 21 Oct 2010 15:54:48 -0700
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Hi Dan,

      Sorry for the late reply since we were busy in our college academics.
We would be doing this project (support for hugepages in tmem) and
soon will be submit our design to this community.
      We have gone through the code of hugepages or superpages support
in Xen. We found that whenever a domain requests a page of order = 0 or
order = 9, it tries to allocate super page or singleton page. No code exists
for order > 0 and order < 9.

       In our study, we also came across a point that if a domain requests a
2 MB page and it gets one, then the domain will not receive 4 KB page during
its stay , which means that a single domain cannot have simultaneous support
to both normal page and super pages. Is it really so? 
      Some part of the code says that if it’s not possible to allocate super 

then it allocates a linked list consisting of 512 4kB pages i.e. from 

or 2M->4k). The performance is improved in case of huge pages due to its
contiguity. But in the case above, does it mean that the performance is 

I think that in design consideration we need to solve this problem of splitting.

According to code such splitting is done in HAP, so what exactly happens in 
shadow mode?

With Regards,
Ashwin Vasani
B.E. (Fourth Year)
Computer  Engineering,
Pune Institute of Computer Technology.
+91 9960405802

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