[Xen-devel] [PATCH] tools/libxc: Document checkpoint compression in xg_save_restore.h

[Shriram Rajagopalan <rshriram@xxxxxxxxx>]

# HG changeset patch
# User Shriram Rajagopalan <rshriram@xxxxxxxxx>
# Date 1308790913 25200
# Node ID 8bef913a3c4d14d2246086ef30a8e80f45ad1beb
# Parent  9eed27800ff6a2e6d73f138f20af072c1b41925e
tools/libxc: Document checkpoint compression in xg_save_restore.h

Add comments to xg_save_restore.h explaining changes in Remus
wire protocol when checkpoint compression is enabled.

Signed-off-by: Shriram Rajagopalan <rshriram@xxxxxxxxx>

diff -r 9eed27800ff6 -r 8bef913a3c4d tools/libxc/xg_save_restore.h
--- a/tools/libxc/xg_save_restore.h     Wed Jun 22 06:34:55 2011 -0700
+++ b/tools/libxc/xg_save_restore.h     Wed Jun 22 18:01:53 2011 -0700
@@ -82,9 +82,24 @@
  *     page data        : PAGE_SIZE bytes for each page marked present in PFN
  *                        array
  *
+ * In case of Remus with checkpoint compression, since the compressed page data
+ * can be of variable size, only the pfn array is sent with a +ve chunk type.
+ *
  * If the chunk type is -ve then chunk consists of one of a number of
  * metadata types.  See definitions of XC_SAVE_ID_* below.
  *
+ * If the chunk type is -ve and equals XC_SAVE_ID_COMPRESSED_DATA, then the
+ * chunk consists of compressed page data, in the following format:
+ *
+ *     unsigned long        : Size of the compressed chunk to follow
+ *     compressed page data : variable length data of size indicated above.
+ *                            This chunk consists of compressed page data. The
+ *                            number of pages in one chunk varies with respect
+ *                            to amount of space available in the sender's
+ *                            output buffer.
+ *
+ * There can be one or more chunks with type XC_SAVE_ID_COMPRESSED_DATA.
+ *
  * If chunk type is 0 then body phase is complete.
  *
  * TAIL PHASE

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