Commit bd6952a3 authored by Denis V. Lunev's avatar Denis V. Lunev Committed by Stefan Hajnoczi
Browse files

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: default avatarDenis V. Lunev <den@openvz.org>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Message-id: 20170725143923.11241-1-den@openvz.org
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Lluís Vilanova <vilanova@ac.upc.edu>
CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 8908eb1a

monitor.c

+5 −4
Original line number Diff line number Diff line
@@ -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);

    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);