From patchwork Wed Apr 6 18:34:43 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?Q?Llu=C3=ADs?= X-Patchwork-Id: 90051 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 17AFFB6F07 for ; Thu, 7 Apr 2011 04:40:28 +1000 (EST) Received: from localhost ([127.0.0.1]:43030 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q7Xe3-0005ka-Di for incoming@patchwork.ozlabs.org; Wed, 06 Apr 2011 14:39:59 -0400 Received: from [140.186.70.92] (port=43217 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q7Xa1-0004M2-IV for qemu-devel@nongnu.org; Wed, 06 Apr 2011 14:35:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q7Xa0-0001oQ-DR for qemu-devel@nongnu.org; Wed, 06 Apr 2011 14:35:49 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:54402) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1Q7Xa0-0001o0-2K for qemu-devel@nongnu.org; Wed, 06 Apr 2011 14:35:48 -0400 Received: (qmail invoked by alias); 06 Apr 2011 18:35:46 -0000 Received: from unknown (EHLO localhost) [84.88.53.92] by mail.gmx.net (mp012) with SMTP; 06 Apr 2011 20:35:46 +0200 X-Authenticated: #12333383 X-Provags-ID: V01U2FsdGVkX19fH3tKydVfwy5yRtqRlT4aRxMaSfi2mmJJFxvROE 3H2Io8hgnbgcYH To: qemu-devel@nongnu.org From: =?utf-8?b?TGx1w61z?= Date: Wed, 06 Apr 2011 20:34:43 +0200 Message-ID: <20110406183443.22854.56246.stgit@ginnungagap.bsc.es> In-Reply-To: <20110406183341.22854.93929.stgit@ginnungagap.bsc.es> References: <20110406183341.22854.93929.stgit@ginnungagap.bsc.es> User-Agent: StGit/0.15 MIME-Version: 1.0 X-Y-GMX-Trusted: 0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-Received-From: 213.165.64.22 Cc: stefanha@gmail.com, chouteau@adacore.com Subject: [Qemu-devel] [PATCH v2 07/11] trace-state: always use the "nop" backend on events with the "disable" keyword X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Any event with the keyword/property "disable" generates an empty trace event using the "nop" backend, regardless of the current backend. Signed-off-by: Lluís Vilanova --- docs/tracing.txt | 25 +++++++++++++++---------- scripts/tracetool | 15 ++------------- 2 files changed, 17 insertions(+), 23 deletions(-) diff --git a/docs/tracing.txt b/docs/tracing.txt index a9fd85b..9138dca 100644 --- a/docs/tracing.txt +++ b/docs/tracing.txt @@ -12,15 +12,11 @@ for debugging, profiling, and observing execution. ./configure --trace-backend=simple make -2. Enable trace events you are interested in: - - $EDITOR trace-events # remove "disable" from events you want - -3. Run the virtual machine to produce a trace file: +2. Run the virtual machine to produce a trace file: qemu ... # your normal QEMU invocation -4. Pretty-print the binary trace file: +3. Pretty-print the binary trace file: ./simpletrace.py trace-events trace-* @@ -98,10 +94,11 @@ portability macros, ensure they are preceded and followed by double quotes: 4. Name trace events after their function. If there are multiple trace events in one function, append a unique distinguisher at the end of the name. -5. Declare trace events with the "disable" property. Some trace events can - produce a lot of output and users are typically only interested in a subset - of trace events. Marking trace events disabled by default saves the user - from having to manually disable noisy trace events. +5. If specific trace events are going to be called a huge number of times, this + might have a noticeable performance impact even when the trace events are + programmatically disabled. In this case you should declare the trace event + with the "disable" property, which will effectively disable it at compile + time (using the "nop" backend). == Trace backends == @@ -126,6 +123,9 @@ The "nop" backend generates empty trace event functions so that the compiler can optimize out trace events completely. This is the default and imposes no performance penalty. +Note that regardless of the selected trace backend, events with the "disable" +property will be generated with the "nop" backend. + === Stderr === The "stderr" backend sends trace events directly to standard error. This @@ -134,6 +134,11 @@ effectively turns trace events into debug printfs. This is the simplest backend and can be used together with existing code that uses DPRINTF(). +Note that with this backend trace events cannot be programmatically +enabled/disabled. Thus, in order to trim down the amount of output and the +performance impact of tracing, you might want to add the "disable" property in +the "trace-events" file for those events you are not interested in. + === Simpletrace === The "simple" backend supports common use cases and comes as part of the QEMU diff --git a/scripts/tracetool b/scripts/tracetool index 6d8ead2..7506776 100755 --- a/scripts/tracetool +++ b/scripts/tracetool @@ -506,21 +506,10 @@ convert() # Skip comments and empty lines test -z "${str%%#*}" && continue + echo # Process the line. The nop backend handles disabled lines. - disable="0" if has_property "$str" "disable"; then - disable="1" - fi - echo - if [ "$disable" = "1" ]; then - # Pass the disabled state as an arg for the simple - # or DTrace backends which handle it dynamically. - # For all other backends, call lineto$1_nop() - if [ $backend = "simple" -o "$backend" = "dtrace" ]; then - "$process_line" "$str" - else - "lineto$1_nop" "${str##disable }" - fi + "lineto$1_nop" "$str" else "$process_line" "$str" fi