[Xen-devel] [PATCH 09 of 27 V4] libxl: drop 8M slack for PV guests

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1330533035 0
# Node ID 096829acb3693eb30787ad859775adb9064fe42c
# Parent  94609c13694b3db49f4da73cdfb3cacb16d597cc
libxl: drop 8M slack for PV guests.

This serves no purpose. It relates to the old 8M to "account for backend
allocations" which we used to add. This leaves a bit of unpopulated space in
the Pseudo-physical address space which can be used by backends when mapping
foreign memory. However 8M is not representative of that any more and modern
kernels do not operate in this way anyway.

I suspect an argument could be made for removing this from the libxl API
altogether but instead lets just set the overhead to 0.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

diff -r 94609c13694b -r 096829acb369 tools/libxl/libxl_create.c
--- a/tools/libxl/libxl_create.c        Wed Feb 29 16:30:35 2012 +0000
+++ b/tools/libxl/libxl_create.c        Wed Feb 29 16:30:35 2012 +0000
@@ -108,7 +108,7 @@ void libxl_domain_build_info_init(libxl_
         b_info->u.hvm.xen_platform_pci = 1;
         break;
     case LIBXL_DOMAIN_TYPE_PV:
-        b_info->u.pv.slack_memkb = 8 * 1024;
+        b_info->u.pv.slack_memkb = 0;
         break;
     default:
         abort();

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