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authorDavid Vrabel <david.vrabel@citrix.com>2011-08-19 15:57:16 +0100
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2011-09-01 09:41:40 -0400
commitd312ae878b6aed3912e1acaaf5d0b2a9d08a4f11 (patch)
treec175aa92b7f7771698052d1b36f52becf21d3c2a /arch/x86
parent60c5f08e154fd235056645e050f2cd5671b19125 (diff)
xen: use maximum reservation to limit amount of usable RAM
Use the domain's maximum reservation to limit the amount of extra RAM for the memory balloon. This reduces the size of the pages tables and the amount of reserved low memory (which defaults to about 1/32 of the total RAM). On a system with 8 GiB of RAM with the domain limited to 1 GiB the kernel reports: Before: Memory: 627792k/4472000k available After: Memory: 549740k/11132224k available A increase of about 76 MiB (~1.5% of the unused 7 GiB). The reserved low memory is also reduced from 253 MiB to 32 MiB. The total additional usable RAM is 329 MiB. For dom0, this requires at patch to Xen ('x86: use 'dom0_mem' to limit the number of pages for dom0') (c/s 23790) CC: stable@kernel.org Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/xen/setup.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 02ffd9e48c9f..ff3dfa176814 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -183,6 +183,19 @@ static unsigned long __init xen_set_identity(const struct e820entry *list,
PFN_UP(start_pci), PFN_DOWN(last));
return identity;
}
+
+static unsigned long __init xen_get_max_pages(void)
+{
+ unsigned long max_pages = MAX_DOMAIN_PAGES;
+ domid_t domid = DOMID_SELF;
+ int ret;
+
+ ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, &domid);
+ if (ret > 0)
+ max_pages = ret;
+ return min(max_pages, MAX_DOMAIN_PAGES);
+}
+
/**
* machine_specific_memory_setup - Hook for machine specific memory setup.
**/
@@ -291,6 +304,12 @@ char * __init xen_memory_setup(void)
sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
+ extra_limit = xen_get_max_pages();
+ if (extra_limit >= max_pfn)
+ extra_pages = extra_limit - max_pfn;
+ else
+ extra_pages = 0;
+
extra_pages += xen_return_unused_memory(xen_start_info->nr_pages, &e820);
/*

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