From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41616) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bX92J-0007cI-GV for qemu-devel@nongnu.org; Tue, 09 Aug 2016 11:33:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bX92H-00062N-Rx for qemu-devel@nongnu.org; Tue, 09 Aug 2016 11:33:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50968) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bX92H-000627-H7 for qemu-devel@nongnu.org; Tue, 09 Aug 2016 11:33:45 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0D22E80B56 for ; Tue, 9 Aug 2016 15:33:45 +0000 (UTC) From: "Daniel P. Berrange" Date: Tue, 9 Aug 2016 16:32:28 +0100 Message-Id: <1470756748-18933-61-git-send-email-berrange@redhat.com> In-Reply-To: <1470756748-18933-1-git-send-email-berrange@redhat.com> References: <1470756748-18933-1-git-send-email-berrange@redhat.com> Subject: [Qemu-devel] [PATCH for-2.8 v1 60/60] trace: update docs to reflect new code generation approach List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , "Daniel P. Berrange" Describe use of per-subdir trace events files and how it impacts code generation. Signed-off-by: Daniel P. Berrange --- docs/tracing.txt | 61 +++++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 52 insertions(+), 9 deletions(-) diff --git a/docs/tracing.txt b/docs/tracing.txt index 29f2f9a..b7ba179 100644 --- a/docs/tracing.txt +++ b/docs/tracing.txt @@ -27,18 +27,51 @@ for debugging, profiling, and observing execution. == Trace events == +=== Sub-directory setup === + Each directory in the source tree can declare a set of static trace events -in a "trace-events" file. Each trace event declaration names the event, its -arguments, and the format string which can be used for pretty-printing: +in a "trace-events" file. The first (non-comment) statement in the file +must be "@id_offset(NN)" where NN is an integer that is unique among all +"trace-events" files in the QEMU source tree. The IDs can be arbitrarily +chosen, but extra fun the current "trace-events" files use values from the +"powerful number" integer sequence :-) - qemu_vmalloc(size_t size, void *ptr) "size %zu ptr %p" - qemu_vfree(void *ptr) "ptr %p" +Any subdirectory which contains a "trace-events" file must be listed in the +"trace-events-subdirs" make variable in the top level Makefile.objs. During +build, the "trace-events" file in each listed subdirectory will be processed +by the "tracetool" script to generate code for the trace events. + +The individual "trace-events" files are merged together into a "trace-events-all" +file, which is also installed into "/usr/share/qemu" with the name "trace-events". +This merge file is to be used by the "simpletrace.py" script to later analyse +traces in the simpletrace data format. + +The Makefile.objs in the subdirectory should have two lines added + + trace-obj-y += trace.o + trace-obj-$(CONFIG_TRACE_DTRACE) += trace-dtrace.o + +In the sub-directory the following files will be automatically generated + + - trace.c - the trace event state declarations + - trace.h - the trace event enums and probe functions + - trace-dtrace.h - DTrace speci + - trace-dtrace.dtrace - DTrace event probe helper declaration + - trace-dtrace.o - binary DTrace provider (generated by dtrace) + - trace-ust.h - UST event probe helper declarations + +Source files in the sub-directory should only #include the 'trace.h' +file and use the full sub-directory path. eg io/channel-buffer.c +would do -All "trace-events" files must be listed in the "trace-event-y" make variable -in the top level Makefile.objs. During build the individual files are combined -to create a "trace-events-all" file, which is processed by the "tracetool" -script during build to generate code for the trace events. The -"trace-events-all" file is also installed into "/usr/share/qemu". + #include "io/trace.h" + +While it is permited to include a trace.h file from outside a source +files' own sub-directory, this is discouraged in general. It is strongly +preferred that all events be declared directly in the sub-directory that +uses them. + +=== Using trace events === Trace events are invoked directly from source code like this: @@ -83,6 +116,13 @@ Format strings should reflect the types defined in the trace event. Take special care to use PRId64 and PRIu64 for int64_t and uint64_t types, respectively. This ensures portability between 32- and 64-bit platforms. +Each event declaration will start with the event name, then its arguments, +finally a format string for pretty-printing. For example: + + qemu_vmalloc(size_t size, void *ptr) "size %zu ptr %p" + qemu_vfree(void *ptr) "ptr %p" + + === Hints for adding new trace events === 1. Trace state changes in the code. Interesting points in the code usually @@ -357,6 +397,9 @@ information. If used together with the "tcg" property, it adds a second "TCGv_env" argument that must point to the per-target global TCG register that points to the vCPU when guest code is executed (usually the "cpu_env" variable). +All "vcpu" events *must* be declared in the top level "trace-events" file. It +is not permitted to have them declared in sub-directories. + The following example events: foo(uint32_t a) "a=%x" -- 2.7.4