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Re: [Xen-devel] [PATCH 00/18] xenpaging changes for 4.0

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 00/18] xenpaging changes for 4.0
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Fri, 22 Oct 2010 10:55:42 +0200
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
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On Fri, Oct 15, Dan Magenheimer wrote:

> Hi Olaf --
> Since you have obviously become an expert user of xenpaging,
> any chance you could write brief how-to documentation for it
> and maybe add a file to xen.hg/docs/misc?

This is a first draft.

Subject: xenpaging: (sparse) documenation

Write up some sparse documentation about xenpaging usage.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

 docs/misc/xenpaging.txt |   40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

--- /dev/null
+++ xen-4.0.1-testing/docs/misc/xenpaging.txt
@@ -0,0 +1,40 @@
+The xenpaging code is new and not fully debugged.
+Usage of xenpaging can crash Xen or cause severe data corruption in the
+guest memory and its filesystems!
+xenpaging writes memory pages of a given guest to a file and moves the
+page back to the pool of available memory.  Once the guests wants to
+access the paged-out memory, the page is read from disk and placed into
+memory.  This allows the sum of all running guests to use more memory
+than physically available on the host.
+Once the guest is running, run xenpaging with the guest_id and the
+number of pages to page-out:
+  mkdir /var/lib/xen/xenpaging
+  chdir /var/lib/xen/xenpaging
+  xenpaging <guest_id>  <number_of_pages>
+To obtain the guest_id, run 'xm list'.
+xenpaging will write the pagefile to the current directory.
+Example with 128MB pagefile on guest 1:
+  xenpaging 1 32768
+Caution: stopping xenpaging manually will cause the guest to stall or
+crash because the paged-out memory is not written back into the guest!
+- implement stopping of xenpaging
+- implement/test live migration
+# vim: tw=72

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