Hi Ian,
On 05/02/2015 18:52, Ian Campbell wrote:
... 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.campb...@citrix.com>
Cc: Jintack Lim <jint...@cs.columbia.edu>
Cc: Jan Beulich <jbeul...@suse.com>
---
v2:
- Use xenheap_megabytes as the option, which is what older x86 Xen
used.
I'd like to backport at least the command line option to 4.5. Reducing
the default heap size is a bit border line but I'm inclined to take
it.
I don't think it will introduce performance regression. So I don't mind
if you backport the whole patch.
---
docs/misc/xen-command-line.markdown | 8 ++++++++
xen/arch/arm/setup.c | 25 ++++++++++++++++++-------
2 files changed, 26 insertions(+), 7 deletions(-)
diff --git a/docs/misc/xen-command-line.markdown
b/docs/misc/xen-command-line.markdown
index bc316be..0a99d1a 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -237,6 +237,14 @@ 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: `1/32 RAM`
+
+Amount of RAM to set aside for the Xenheap. By default 1/32 of the RAM
+up to a maximum of 1GB and with a minimum of 32M.
+
### clocksource
> `= pit | hpet | acpi`
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index a916ca6..73691c0 100644
--- 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();
@@ -501,16 +506,21 @@ static void __init setup_mm(unsigned long dtb_paddr,
size_t dtb_size)
*
* - 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 )
If the user requests a xenheap of 0MB, we will use the default size,
right? It may be worth to explain this case.
Also with the algorithm to find a range, the Xen heap may be smaller. I
would explain that too.
+ 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
{
You seem to have forgotten to update the condition in the do/while:
xenheap_pages > 128 << (20 - PAGE_SHIFT);
Regards,
--
Julien Grall
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