cli: Add --iothreads defaultiothread.thread_pool_{min,max}

It allows to set the thread pool size to optimize spawning worker threads
for the default event loop in real time environment. For example:

--iothreads defaultiothread.thread_pool_min=8,\
defaultiothread.thread_pool_max=16

Signed-off-by: Lin Ma <lma@suse.com>

tests/data/cli/compare/virt-install-many-devices.xml

@@ -14,6 +14,7 @@
     <iothread id="1"/>
     <iothread id="2" thread_pool_min="8" thread_pool_max="16"/>
   </iothreadids>
+  <defaultiothread thread_pool_min="4" thread_pool_max="32"/>
   <memory>65536</memory>
   <currentMemory>65536</currentMemory>
   <blkiotune>

tests/test_cli.py

@@ -545,7 +545,7 @@ memorytune0.vcpus=0-3,memorytune0.node0.id=0,memorytune0.node0.bandwidth=60
 --memorybacking size=1,unit='G',nodeset=0,1,nosharepages=yes,locked=yes,discard=yes,allocation.mode=immediate,access_mode=shared,source_type=file,hugepages.page.size=12,hugepages.page1.size=1234,hugepages.page1.unit=MB,hugepages.page1.nodeset=2,allocation.threads=8
 
 
---iothreads iothreads=5,iothreadids.iothread0.id=1,iothreadids.iothread1.id=2,iothreadids.iothread1.thread_pool_min=8,iothreadids.iothread1.thread_pool_max=16
+--iothreads iothreads=5,iothreadids.iothread0.id=1,iothreadids.iothread1.id=2,iothreadids.iothread1.thread_pool_min=8,iothreadids.iothread1.thread_pool_max=16,defaultiothread.thread_pool_min=4,defaultiothread.thread_pool_max=32
 
 
 --metadata title=my-title,description=my-description,uuid=00000000-1111-2222-3333-444444444444,genid=e9392370-2917-565e-692b-d057f46512d6,genid_enable=yes

virtinst/cli.py

@@ -2608,6 +2608,12 @@ class ParserIOThreads(VirtCLIParser):
         cb = self._make_find_inst_cb(cliarg, list_propname)
         return cb(*args, **kwargs)
 
+    def defaultiothread_find_inst_cb(self, *args, **kwargs):
+        cliarg = "defaultiothread"
+        list_propname = "defaultiothread"
+        cb = self._make_find_inst_cb(cliarg, list_propname)
+        return cb(*args, **kwargs)
+
     @classmethod
     def _virtcli_class_init(cls):
         VirtCLIParser._virtcli_class_init_common(cls)
@@ -2619,6 +2625,10 @@ class ParserIOThreads(VirtCLIParser):
                     "thread_pool_min", find_inst_cb=cls.iothreads_find_inst_cb)
         cls.add_arg("iothreadids.iothread[0-9]*.thread_pool_max",
                     "thread_pool_max", find_inst_cb=cls.iothreads_find_inst_cb)
+        cls.add_arg("defaultiothread.thread_pool_min", "thread_pool_min",
+                    find_inst_cb=cls.defaultiothread_find_inst_cb)
+        cls.add_arg("defaultiothread.thread_pool_max", "thread_pool_max",
+                    find_inst_cb=cls.defaultiothread_find_inst_cb)
 
 
 ###################

virtinst/guest.py

@@ -74,6 +74,13 @@ class _IOThreadID(XMLBuilder):
     thread_pool_max = XMLProperty("./@thread_pool_max", is_int=True)
 
 
+class _DefaultIOThread(XMLBuilder):
+    XML_NAME = "defaultiothread"
+
+    thread_pool_min = XMLProperty("./@thread_pool_min", is_int=True)
+    thread_pool_max = XMLProperty("./@thread_pool_max", is_int=True)
+
+
 class Guest(XMLBuilder):
     @staticmethod
     def validate_name(conn, name, check_collision=True, validate=True):
@@ -180,7 +187,8 @@ class Guest(XMLBuilder):
     XML_NAME = "domain"
     _XML_PROP_ORDER = [
         "type", "name", "uuid", "genid", "genid_enable",
-        "title", "description", "_metadata", "iothreads", "iothreadids",
+        "title", "description", "_metadata",
+        "iothreads", "iothreadids", "defaultiothread",
         "maxMemory", "maxMemorySlots", "memory", "_currentMemory",
         "blkiotune", "memtune", "memoryBacking",
         "_vcpus", "vcpu_current", "vcpu_placement",
@@ -226,6 +234,7 @@ class Guest(XMLBuilder):
 
     iothreads = XMLProperty("./iothreads", is_int=True)
     iothreadids = XMLChildProperty(_IOThreadID, relative_xpath="./iothreadids")
+    defaultiothread = XMLChildProperty(_DefaultIOThread)
 
     def _set_currentMemory(self, val):
         if val is not None: