From: Jarod Wilson <jwilson@redhat.com>
Date: Fri, 10 Aug 2007 13:02:18 -0400
Subject: [xen] ia64: saner default mem and cpu alloc for dom0
Message-id: 46BC9A1A.9030004@redhat.com
O-Subject: Re: [UPDATED RHEL5.1 PATCH] ia64 xen: saner default mem and cpu alloc for dom0
Bugzilla: 248967

>>> At present, ia64 xen's dom0 comes up on only 512MB of RAM and one cpu,
>>> unlike other arches, that come up on all memory and all cpus. However,
>>> that can't reasonably be done (yet) on ia64, because the memory and cpu
>>> counts can be so large, xen just falls on its face. For reference, see:
>>>
>>>
http://www.binarytag.com/EXMAIL/mailinglists/binarytag_xen-ia64-devel/msg00182.html

--
Jarod Wilson
jwilson@redhat.com

[IA64] Saner dom0 memory and cpu defaults

Some ia64 xen dom0 tweaks:
* Increase default memory allocation from 512M to 4G
* Increase default vcpu allocation from 1 to 4
* Implement rough calculation of what the maximum memory
  that can be safely allocated to dom0 is
* If need be, scale down requested memory allocation to fit
  available memory, rather than simply panicking
* If dom0_mem=0 is specified, allocate all available mem

Signed-off-by: Jarod Wilson <jwilson@redhat.com>

diff --git a/arch/ia64/xen/domain.c b/arch/ia64/xen/domain.c
index d4aed1d..bb69b8d 100644
--- a/arch/ia64/xen/domain.c
+++ b/arch/ia64/xen/domain.c
@@ -52,10 +52,11 @@
 #include <asm/perfmon.h>
 #include <public/vcpu.h>
 
-unsigned long dom0_size = 512*1024*1024;
+/* dom0_size: default memory allocation for dom0 (~4GB) */
+unsigned long dom0_size = 4096UL*1024UL*1024UL;
 
 /* dom0_max_vcpus: maximum number of VCPUs to create for dom0.  */
-static unsigned int dom0_max_vcpus = 1;
+static unsigned int dom0_max_vcpus = 4;
 integer_param("dom0_max_vcpus", dom0_max_vcpus); 
 
 extern unsigned long running_on_sim;
@@ -1015,8 +1016,41 @@ static void loaddomainelfimage(struct domain *d, struct elf_binary *elf)
 	}
 }
 
-void alloc_dom0(void)
+static void calc_dom0_size(void)
 {
+	unsigned long domheap_pages;
+	unsigned long p2m_pages;
+	unsigned long spare_hv_pages;
+	unsigned long max_dom0_size;
+
+	/* Estimate maximum memory we can safely allocate for dom0
+	 * by subtracting the p2m table allocation and a chunk of memory
+	 * for DMA and PCI mapping from the available domheap pages. The
+	 * chunk for DMA, PCI, etc., is a guestimate, as xen doesn't seem
+	 * to have a good idea of what those requirements might be ahead
+	 * of time, calculated at 1MB per 4GB of system memory */
+	domheap_pages = avail_domheap_pages();
+	p2m_pages = domheap_pages / PTRS_PER_PTE;
+	spare_hv_pages = domheap_pages / 4096;
+	max_dom0_size = (domheap_pages - (p2m_pages + spare_hv_pages))
+			 * PAGE_SIZE;
+	printk("Maximum permitted dom0 size: %luMB\n",
+	       max_dom0_size / (1024*1024));
+
+	/* validate proposed dom0_size, fix up as needed */
+	if (dom0_size > max_dom0_size) {
+		printk("Reducing dom0 memory allocation from %luK to %luK "
+		       "to fit available memory\n",
+		       dom0_size / 1024, max_dom0_size / 1024);
+		dom0_size = max_dom0_size;
+	}
+
+	/* dom0_mem=0 can be passed in to give all available mem to dom0 */
+	if (dom0_size == 0) {
+		printk("Allocating all available memory to dom0\n");
+		dom0_size = max_dom0_size;
+	}
+
 	/* Check dom0 size.  */
 	if (dom0_size < 4 * 1024 * 1024) {
 		panic("dom0_mem is too small, boot aborted"
@@ -1081,6 +1115,8 @@ int construct_dom0(struct domain *d,
 
 	printk("*** LOADING DOMAIN 0 ***\n");
 
+	calc_dom0_size();
+
 	max_pages = dom0_size / PAGE_SIZE;
 	d->max_pages = max_pages;
 	d->tot_pages = 0;
diff --git a/arch/ia64/xen/xensetup.c b/arch/ia64/xen/xensetup.c
index fe067ff..ca6727a 100644
--- a/arch/ia64/xen/xensetup.c
+++ b/arch/ia64/xen/xensetup.c
@@ -46,7 +46,6 @@ extern long is_platform_hp_ski(void);
 extern void early_setup_arch(char **);
 extern void late_setup_arch(char **);
 extern void hpsim_serial_init(void);
-extern void alloc_dom0(void);
 extern void setup_per_cpu_areas(void);
 extern void mem_init(void);
 extern void init_IRQ(void);
@@ -409,8 +408,6 @@ void start_kernel(void)
 
     trap_init();
 
-    alloc_dom0();
-
     init_xenheap_pages(__pa(xen_heap_start), xenheap_phys_end);
     printk("Xen heap: %luMB (%lukB)\n",
 	(xenheap_phys_end-__pa(xen_heap_start)) >> 20,