[libvirt] [PATCH] cpumap: optimize for clients that don't need online count

[Eric Blake]

It turns out that calling virNodeGetCPUMap(conn, NULL, NULL, 0)
is both useful, and with Viktor's patches, common enough to
optimize.  Since this interface hasn't been released yet, we
can change the RPC call.

* src/nodeinfo.c (nodeGetCPUMap): Avoid bitmap when not needed.
* src/remote/remote_protocol.x (remote_node_get_cpu_map_args):
Supply two separate flags for needed arguments.
* src/remote/remote_driver.c (remoteNodeGetCPUMap): Update
caller.
* daemon/remote.c (remoteDispatchNodeGetCPUMap): Likewise.
* src/remote_protocol-structs: Regenerate.
---

This has to be applied before 1.0.0 if we want it; otherwise the
change to RPC wire protocol will render this patch an ABI break.

I thought of one alternative, that wouldn't change the RPC size,
but still would be a difference.  That would be using the old
need_results int as a bitmap of which of the two arguments are
needed, instead of just a 1 or 0.  But even that is risky enough
that it should get in before we commit to this interface.

 daemon/remote.c              | 8 ++++----
 src/nodeinfo.c               | 3 +++
 src/remote/remote_driver.c   | 3 ++-
 src/remote/remote_protocol.x | 3 ++-
 src/remote_protocol-structs  | 3 ++-
 5 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/daemon/remote.c b/daemon/remote.c
index 7a9df60..340d07d 100644
--- a/daemon/remote.c
+++ b/daemon/remote.c
@@ -4578,7 +4578,7 @@ remoteDispatchNodeGetCPUMap(virNetServerPtr server ATTRIBUTE_UNUSED,
                             remote_node_get_cpu_map_ret *ret)
 {
     unsigned char *cpumap = NULL;
-    unsigned int online;
+    unsigned int online = 0;
     unsigned int flags;
     int cpunum;
     int rv = -1;
@@ -4592,13 +4592,13 @@ remoteDispatchNodeGetCPUMap(virNetServerPtr server ATTRIBUTE_UNUSED,

     flags = args->flags;

-    cpunum = virNodeGetCPUMap(priv->conn, args->need_results ? &cpumap : NULL,
-                              &online, flags);
+    cpunum = virNodeGetCPUMap(priv->conn, args->need_map ? &cpumap : NULL,
+                              args->need_online ? &online : NULL, flags);
     if (cpunum < 0)
         goto cleanup;

     /* 'serialize' return cpumap */
-    if (args->need_results) {
+    if (args->need_map) {
         ret->cpumap.cpumap_len = VIR_CPU_MAPLEN(cpunum);
         ret->cpumap.cpumap_val = (char *) cpumap;
         cpumap = NULL;
diff --git a/src/nodeinfo.c b/src/nodeinfo.c
index 35c5f96..3348ae7 100644
--- a/src/nodeinfo.c
+++ b/src/nodeinfo.c
@@ -1277,6 +1277,9 @@ nodeGetCPUMap(virConnectPtr conn ATTRIBUTE_UNUSED,

     virCheckFlags(0, -1);

+    if (!cpumap && !online)
+        return nodeGetCPUCount();
+
     if (!(cpus = nodeGetCPUBitmap(&maxpresent)))
         goto cleanup;

diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c
index 71218f0..5eca0fa 100644
--- a/src/remote/remote_driver.c
+++ b/src/remote/remote_driver.c
@@ -5793,7 +5793,8 @@ remoteNodeGetCPUMap(virConnectPtr conn,

     remoteDriverLock(priv);

-    args.need_results = !!cpumap;
+    args.need_map = !!cpumap;
+    args.need_online = !!online;
     args.flags = flags;

     memset (&ret, 0, sizeof(ret));
diff --git a/src/remote/remote_protocol.x b/src/remote/remote_protocol.x
index 765ffcd..d6ac3c1 100644
--- a/src/remote/remote_protocol.x
+++ b/src/remote/remote_protocol.x
@@ -2671,7 +2671,8 @@ struct remote_node_get_memory_parameters_ret {
 };

 struct remote_node_get_cpu_map_args {
-    int need_results;
+    int need_map;
+    int need_online;
     unsigned int flags;
 };

diff --git a/src/remote_protocol-structs b/src/remote_protocol-structs
index 567864a..6fe7213 100644
--- a/src/remote_protocol-structs
+++ b/src/remote_protocol-structs
@@ -2127,7 +2127,8 @@ struct remote_node_get_memory_parameters_ret {
         int                        nparams;
 };
 struct remote_node_get_cpu_map_args {
-        int                        need_results;
+        int                        need_map;
+        int                        need_online;
         u_int                      flags;
 };
 struct remote_node_get_cpu_map_ret {
-- 
1.7.11.7