From: Denis V. Lunev Date: Tue, 25 Jul 2017 14:39:23 +0000 (+0300) Subject: monitor: Reduce handle_qmp_command() tracing overhead X-Git-Tag: v2.10.0-rc1~6^2 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=bd6952a391b6f2083d6597386f457f30044e32a3;p=users%2Fdwmw2%2Fqemu.git monitor: Reduce handle_qmp_command() tracing overhead We are malloc'ing a QString and spending CPU cycles on converting a QObject to string, just for the sake of sticking the string in the trace message. Wasted when we aren't tracing. Avoid that. [Commit message and description suggested by Markus Armbruster to provide more detail about the rationale for this patch. Use trace_event_get_state_backends() instead of trace_event_get_state() to honor DTrace/UST backend dstates. --Stefan] Signed-off-by: Denis V. Lunev Reviewed-by: Eric Blake Message-id: 20170725143923.11241-1-den@openvz.org CC: Stefan Hajnoczi CC: Lluís Vilanova CC: Dr. David Alan Gilbert CC: Markus Armbruster Signed-off-by: Stefan Hajnoczi --- diff --git a/monitor.c b/monitor.c index 6d040e620f..e0f880107f 100644 --- a/monitor.c +++ b/monitor.c @@ -3823,7 +3823,6 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens) QDict *qdict = NULL; Monitor *mon = cur_mon; Error *err = NULL; - QString *req_json; req = json_parser_parse_err(tokens, NULL, &err); if (!req && !err) { @@ -3841,9 +3840,11 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens) qdict_del(qdict, "id"); } /* else will fail qmp_dispatch() */ - req_json = qobject_to_json(req); - trace_handle_qmp_command(mon, qstring_get_str(req_json)); - QDECREF(req_json); + if (trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) { + QString *req_json = qobject_to_json(req); + trace_handle_qmp_command(mon, qstring_get_str(req_json)); + QDECREF(req_json); + } rsp = qmp_dispatch(cur_mon->qmp.commands, req);