[Qemu-devel] [PULL 04/38] s390/sclp: cache the sclp device

[Cornelia Huck <cornelia.huck@de.ibm.com>]

From: Christian Borntraeger <borntraeger@de.ibm.com>

With the current code a simple sclp command takes about 13000 ns
The biggest part seems to be the resolver of the object model. By
caching the sclp device the time for an sclp command goes down to
2500ns. Talking about real life scenarios, this change doubles
the speed of the sclp console when sending single bytes outputs
to /dev/console.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
 hw/s390x/sclp.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index fca37f5..540226c 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -26,7 +26,12 @@
 
 static inline SCLPDevice *get_sclp_device(void)
 {
-    return SCLP(object_resolve_path_type("", TYPE_SCLP, NULL));
+    static SCLPDevice *sclp;
+
+    if (!sclp) {
+        sclp = SCLP(object_resolve_path_type("", TYPE_SCLP, NULL));
+    }
+    return sclp;
 }
 
 /* Provide information about the configuration, CPUs and storage */
-- 
2.9.3