xen: arm32: reduce default size of the xenheap

... and make it tunable via the command line.

1/8 of RAM is 128M on a 1GB system and 256M on a 2GB system etc,
which is a lot. 1/32 of RAM seems more reasonable. Also drop the
minimum to 32M.

Leave the maximum at 1GB.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Julien Grall <julien.grall@linaro.org>
Cc: Jintack Lim <jintack@cs.columbia.edu>
Cc: Jan Beulich <JBeulich@suse.com>

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index bc316beb0156256ff5120fc2bf500e8e5560a668..9b458e182d5f3338eb844f1959b2dd702c0366d9 100644 (file)
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -237,6 +237,17 @@ and not running softirqs. Reduce this if softirqs are not being run frequently
 enough. Setting this to a high value may cause boot failure, particularly if
 the NMI watchdog is also enabled.
 
+### xenheap\_megabytes (arm32)
+> `= <size>`
+
+> Default: `0` (1/32 of RAM)
+
+Amount of RAM to set aside for the Xenheap.
+
+By default will use 1/32 of the RAM up to a maximum of 1GB and with a
+minimum of 32M, subject to a suitably aligned and sized contiguous
+region of memory being available.
+
 ### clocksource
 > `= pit | hpet | acpi`
 

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index a916ca6690f826c51222ad783fc35ea0c38f162b..9a1c28514d559c190d24ff656ca966aac3982721 100644 (file)
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -50,6 +50,11 @@ struct bootinfo __initdata bootinfo;
 
 struct cpuinfo_arm __read_mostly boot_cpu_data;
 
+#ifdef CONFIG_ARM_32
+static unsigned long opt_xenheap_megabytes __initdata;
+integer_param("xenheap_megabytes", opt_xenheap_megabytes);
+#endif
+
 static __used void init_done(void)
 {
     free_init_memory();
@@ -497,20 +502,26 @@ static void __init setup_mm(unsigned long dtb_paddr, size_t dtb_size)
     total_pages = ram_pages = ram_size >> PAGE_SHIFT;
 
     /*
-     * Locate the xenheap using these constraints:
+     * If the user has not requested otherwise via the command line
+     * then locate the xenheap using these constraints:
      *
      *  - must be 32 MiB aligned
      *  - must not include Xen itself or the boot modules
-     *  - must be at most 1GB or 1/8 the total RAM in the system if less
-     *  - must be at least 128M
+     *  - must be at most 1GB or 1/32 the total RAM in the system if less
+     *  - must be at least 32M
      *
      * We try to allocate the largest xenheap possible within these
      * constraints.
      */
     heap_pages = ram_pages;
-    xenheap_pages = (heap_pages/8 + 0x1fffUL) & ~0x1fffUL;
-    xenheap_pages = max(xenheap_pages, 128UL<<(20-PAGE_SHIFT));
-    xenheap_pages = min(xenheap_pages, 1UL<<(30-PAGE_SHIFT));
+    if ( opt_xenheap_megabytes )
+        xenheap_pages = opt_xenheap_megabytes << (20-PAGE_SHIFT);
+    else
+    {
+        xenheap_pages = (heap_pages/32 + 0x1fffUL) & ~0x1fffUL;
+        xenheap_pages = max(xenheap_pages, 32UL<<(20-PAGE_SHIFT));
+        xenheap_pages = min(xenheap_pages, 1UL<<(30-PAGE_SHIFT));
+    }
 
     do
     {
@@ -521,15 +532,16 @@ static void __init setup_mm(unsigned long dtb_paddr, size_t dtb_size)
             break;
 
         xenheap_pages >>= 1;
-    } while ( xenheap_pages > 128<<(20-PAGE_SHIFT) );
+    } while ( !opt_xenheap_megabytes && xenheap_pages > 32<<(20-PAGE_SHIFT) );
 
     if ( ! e )
         panic("Not not enough space for xenheap");
 
     domheap_pages = heap_pages - xenheap_pages;
 
-    printk("Xen heap: %"PRIpaddr"-%"PRIpaddr" (%lu pages)\n",
-            e - (pfn_to_paddr(xenheap_pages)), e, xenheap_pages);
+    printk("Xen heap: %"PRIpaddr"-%"PRIpaddr" (%lu pages%s)\n",
+           e - (pfn_to_paddr(xenheap_pages)), e, xenheap_pages,
+           opt_xenheap_megabytes ? ", from command-line" : "");
     printk("Dom heap: %lu pages\n", domheap_pages);
 
     setup_xenheap_mappings((e >> PAGE_SHIFT) - xenheap_pages, xenheap_pages);