[IA64] improve response time in dom 0 at creating a guest domain

The hypercall takes several hundred mili seconds,
and it takes around 5 mili seconds with my new patch.
Time of one hypercall should be smaller than a vcpu time slice.

Signed-off-by: Akio Takebe <takebe_akio@jp.fujitsu.com>

diff --git a/arch/ia64/xen/xcom_privcmd.c b/arch/ia64/xen/xcom_privcmd.c
index 466180f1301b54d25d179e5b3a3a6605a9c7d650..7b32a0a283d4ea9f95b16ad95ec6c6baa729cd04 100644 (file)
--- a/arch/ia64/xen/xcom_privcmd.c
+++ b/arch/ia64/xen/xcom_privcmd.c
@@ -437,15 +437,18 @@ xencomm_privcmd_memory_reservation_op(privcmd_hypercall_t *hypercall)
                 *   may cause the soft lockup warning.
                 *   In order to avoid the warning, we limit
                 *   the number of extents and repeat the hypercall.
-                *   The following value is determined by experimentation.
-                *   If the following limit causes soft lockup warning,
+                *   The following value is determined by evaluation.
+                *   Time of one hypercall should be smaller than
+                *   a vcpu time slice. The time with current
+                *   MEMORYOP_MAX_EXTENTS is around 5 msec.
+                *   If the following limit causes some issues,
                 *   we should decrease this value.
                 *
                 *   Another way would be that start with small value and
                 *   increase adoptively measuring hypercall time.
                 *   It might be over-kill.
                 */
-#define MEMORYOP_MAX_EXTENTS   (MEMORYOP_XENCOMM_LIMIT / 4)
+#define MEMORYOP_MAX_EXTENTS   (MEMORYOP_XENCOMM_LIMIT / 512)
 
                while (nr_extents > 0) {
                        xen_ulong_t nr_tmp = nr_extents;