[Qemu-devel] [PATCH v2] scripts: qmp: Introduce vcpu pinning helper script

[Maxime Coquelin]

This python script calls 'query-cpus' QMP command to retrieve
vCPUs thread IDs.
Thread IDs are then used by taskset to pin vCPUs to physical
CPUs passed in command line.

In case more vCPUs are present than the number of CPUs assigned
in command line, multiple vCPUs get pinned to physical CPUs.

If multiple vCPUs share a same thread ID (e.g. with TCG), the
thread ID is pinned a single time.

Signed-off-by: Maxime Coquelin <address@hidden>
---
Changes since RFC:
==================
 - If vCPUs share a same TID, don't pin them multiple times (peterx)

 scripts/qmp/qmp-vcpu-pin | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100755 scripts/qmp/qmp-vcpu-pin

diff --git a/scripts/qmp/qmp-vcpu-pin b/scripts/qmp/qmp-vcpu-pin
new file mode 100755
index 0000000..9eefe6e
--- /dev/null
+++ b/scripts/qmp/qmp-vcpu-pin
@@ -0,0 +1,45 @@
+#!/usr/bin/python
+# QEMU vCPU pinning tool
+#
+# Copyright (C) 2016 Red Hat Inc.
+#
+# Authors:
+#  Maxime Coquelin <address@hidden>
+#
+# This work is licensed under the terms of the GNU GPL, version 2.  See
+# the COPYING file in the top-level directory
+import argparse
+import json
+import os
+
+from subprocess import call
+from qmp import QEMUMonitorProtocol
+
+pinned = []
+
+parser = argparse.ArgumentParser(description='Pin QEMU vCPUs to physical CPUs')
+parser.add_argument('-s', '--server', type=str, required=True,
+                    help='QMP server path or address:port')
+parser.add_argument('cpu', type=int, nargs='+',
+                    help='Physical CPUs IDs')
+args = parser.parse_args()
+
+devnull = open(os.devnull, 'w')
+
+srv = QEMUMonitorProtocol(args.server)
+srv.connect()
+
+for vcpu in srv.command('query-cpus'):
+    vcpuid = vcpu['CPU']
+    tid = vcpu['thread_id']
+    if tid in pinned:
+        print 'vCPU{}\'s tid {} already pinned, skipping'.format(vcpuid, tid)
+        continue
+
+    cpuid = args.cpu[vcpuid % len(args.cpu)]
+    print 'Pin vCPU {} (tid {}) to physical CPU {}'.format(vcpuid, tid, cpuid)
+    try:
+        call(['taskset', '-pc', str(cpuid), str(tid)], stdout=devnull)
+        pinned.append(tid)
+    except OSError:
+        print 'Failed to pin vCPU{} to CPU{}'.format(vcpuid, cpuid)
-- 
2.7.4