| Message ID | 20170106155543.12827-47-berrange@redhat.com |
|---|---|
| State | New |
| Headers | show |
Daniel P Berrange writes: > Describe use of per-subdir trace events files and how it impacts > code generation. > Signed-off-by: Daniel P. Berrange <berrange@redhat.com> > --- > docs/tracing.txt | 61 +++++++++++++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 52 insertions(+), 9 deletions(-) > diff --git a/docs/tracing.txt b/docs/tracing.txt > index f351998a..3262a61 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 for extra fun the current "trace-events" files use values from > +the "powerful number" integer sequence :-) I think that the description of @id_offset is a leftover from a previous version of the series. Cheers, Lluis
On 01/06/2017 09:55 AM, Daniel P. Berrange wrote: > Describe use of per-subdir trace events files and how it impacts > code generation. > > Signed-off-by: Daniel P. Berrange <berrange@redhat.com> > --- > docs/tracing.txt | 61 +++++++++++++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 52 insertions(+), 9 deletions(-) > > diff --git a/docs/tracing.txt b/docs/tracing.txt > index f351998a..3262a61 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 for extra fun the current "trace-events" files use values from > +the "powerful number" integer sequence :-) Is this true? I don't see an @id_offset() comment in any of your earlier patches, or in the unpatched tree. > +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 s/speci/specification/ ? > + - 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 s/permited/permitted/ > +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 === >
diff --git a/docs/tracing.txt b/docs/tracing.txt index f351998a..3262a61 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 for 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 @@ -372,6 +412,9 @@ 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"
Describe use of per-subdir trace events files and how it impacts code generation. Signed-off-by: Daniel P. Berrange <berrange@redhat.com> --- docs/tracing.txt | 61 +++++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 52 insertions(+), 9 deletions(-)