xen/xen-lowmem-emergency-pool.diff

Index: xen-unstable/xen/arch/x86/x86_32/mm.c
===================================================================
--- xen-unstable.orig/xen/arch/x86/x86_32/mm.c
+++ xen-unstable/xen/arch/x86/x86_32/mm.c
@@ -63,6 +63,8 @@ l2_pgentry_t *virt_to_xen_l2e(unsigned l
     return &idle_pg_table_l2[l2_linear_offset(v)];
 }
 
+extern unsigned long lowmem_emergency_pool_pages;
+
 void __init paging_init(void)
 {
     void *ioremap_pt;
@@ -131,6 +133,20 @@ void __init setup_idle_pagetable(void)
                   l2e_from_page(virt_to_page(idle_vcpu[0]->domain->
                                              arch.mm_perdomain_pt) + i,
                                 __PAGE_HYPERVISOR));
+
+    /*
+     * Size the lowmem_emergency_pool based on the total memory on the box
+     * This pool is needed only on 32 bit PAE configurations (4g to 16g).
+     */
+    if (lowmem_emergency_pool_pages)
+        return;
+
+    if (total_pages > (4 * 1024 * 1024))
+        lowmem_emergency_pool_pages = 12000;
+    else if (total_pages > (2 * 1024 * 1024))
+        lowmem_emergency_pool_pages = 8000;
+    else if (total_pages > (1 * 1024 * 1024) || max_page >= (1 * 1024 * 1024))
+        lowmem_emergency_pool_pages = 4000;
 }
 
 void __init zap_low_mappings(l2_pgentry_t *base)
Index: xen-unstable/xen/common/page_alloc.c
===================================================================
--- xen-unstable.orig/xen/common/page_alloc.c
+++ xen-unstable/xen/common/page_alloc.c
@@ -46,6 +46,20 @@ static char opt_badpage[100] = "";
 string_param("badpage", opt_badpage);
 
 /*
+ * Amount of memory to reserve in a low-memory (<4GB) pool for specific
+ * allocation requests. Ordinary requests will not fall back to the
+ * lowmem emergency pool.
+ */
+unsigned long lowmem_emergency_pool_pages;
+static void parse_lowmem_emergency_pool(char *s)
+{
+    unsigned long long bytes;
+    bytes = parse_size_and_unit(s, NULL);
+    lowmem_emergency_pool_pages = bytes >> PAGE_SHIFT;
+}
+custom_param("lowmem_emergency_pool", parse_lowmem_emergency_pool);
+
+/*
  * Bit width of the DMA heap.
  */
 static unsigned int  dma_bitsize = CONFIG_DMA_BITSIZE;