From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47741) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aSqvj-0006v8-Tc for qemu-devel@nongnu.org; Mon, 08 Feb 2016 13:53:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aSqve-0002bo-Oz for qemu-devel@nongnu.org; Mon, 08 Feb 2016 13:52:59 -0500 Received: from relay1.mentorg.com ([192.94.38.131]:58573) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aSqve-0002bC-JY for qemu-devel@nongnu.org; Mon, 08 Feb 2016 13:52:54 -0500 From: Hollis Blanchard Date: Mon, 8 Feb 2016 10:51:55 -0800 Message-ID: <1454957515-29258-1-git-send-email-hollis_blanchard@mentor.com> In-Reply-To: <20160208153014.GD31586@stefanha-x1.localdomain> References: <20160208153014.GD31586@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain Subject: [Qemu-devel] [PATCH] trace: only create simple backend trace files when an event is emitted. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: stefanha@gmail.com, Hollis Blanchard Previously, trace record files (created by st_set_trace_file_enabled(true)) were created by the simple backend at initialization time, even if no events were actually enabled. As a consequence, the working directory would become littered with trace-PID files just by enabling the simple backend at configure time, even when no -trace options were used. --- I've been using this to avoid creation of empty trace record files. I haven't done any scientific performance studies, but an extra function call/conditional/return when recording every trace event doesn't seem to have any noticeable effect. Signed-off-by: Hollis Blanchard --- trace/simple.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/trace/simple.c b/trace/simple.c index 3fdcc82..67ccc3c 100644 --- a/trace/simple.c +++ b/trace/simple.c @@ -209,6 +209,8 @@ int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasi uint64_t event_u64 = event; uint64_t timestamp_ns = get_clock(); + st_set_trace_file_enabled(true); + do { old_idx = g_atomic_int_get(&trace_idx); smp_rmb(); @@ -320,6 +322,7 @@ void st_set_trace_file_enabled(bool enable) */ void st_set_trace_file(const char *file) { + /* Tracing will be re-enabled when the next event is written. */ st_set_trace_file_enabled(false); g_free(trace_file_name); @@ -330,8 +333,6 @@ void st_set_trace_file(const char *file) } else { trace_file_name = g_strdup_printf("%s", file); } - - st_set_trace_file_enabled(true); } void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...)) -- 1.9.1