| Message ID | 20200706154714.27566-1-tz.stoyanov@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 6c18ee3436488802638503fa5d2969af3e20f1f4 |
| Headers | show |
| Series | trace-cmd: Fix kbuffer_start_of_data() to return the first record | expand |
On Mon, 6 Jul 2020 18:47:14 +0300 "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote: > The first record in a ring buffer page may not allways be at the > beginning of the page. There could be time-extends injected before it. > In this case kbuffer_start_of_data() will not return the first record, > as expected. Additional filed "start" is added in kbuffer struct, to hold > the offset of the first record from the page and kbuffer_start_of_data() > is modified to use it. Thanks Tzvetomir, I'm going to add a comment that this was originally taken from code I wrote, and you cleaned it up and made it presentable. That way it states why there's the two signed-off-bys. -- Steve > > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> > --- > lib/traceevent/kbuffer-parse.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/lib/traceevent/kbuffer-parse.c b/lib/traceevent/kbuffer-parse.c > index 2c5f00a9..844db976 100644 > --- a/lib/traceevent/kbuffer-parse.c > +++ b/lib/traceevent/kbuffer-parse.c > @@ -35,6 +35,7 @@ enum { > * @next - offset from @data to the start of next event > * @size - The size of data on @data > * @start - The offset from @subbuffer where @data lives > + * @first - The offset from @subbuffer where the first non time stamp event lives > * > * @read_4 - Function to read 4 raw bytes (may swap) > * @read_8 - Function to read 8 raw bytes (may swap) > @@ -51,6 +52,7 @@ struct kbuffer { > unsigned int next; > unsigned int size; > unsigned int start; > + unsigned int first; > > unsigned int (*read_4)(void *ptr); > unsigned long long (*read_8)(void *ptr); > @@ -546,6 +548,9 @@ int kbuffer_load_subbuffer(struct kbuffer *kbuf, void *subbuffer) > > next_event(kbuf); > > + /* save the first record from the page */ > + kbuf->first = kbuf->curr; > + > return 0; > } > > @@ -755,7 +760,7 @@ void kbuffer_set_old_format(struct kbuffer *kbuf) > */ > int kbuffer_start_of_data(struct kbuffer *kbuf) > { > - return kbuf->start; > + return kbuf->first + kbuf->start; > } > > /**
diff --git a/lib/traceevent/kbuffer-parse.c b/lib/traceevent/kbuffer-parse.c index 2c5f00a9..844db976 100644 --- a/lib/traceevent/kbuffer-parse.c +++ b/lib/traceevent/kbuffer-parse.c @@ -35,6 +35,7 @@ enum { * @next - offset from @data to the start of next event * @size - The size of data on @data * @start - The offset from @subbuffer where @data lives + * @first - The offset from @subbuffer where the first non time stamp event lives * * @read_4 - Function to read 4 raw bytes (may swap) * @read_8 - Function to read 8 raw bytes (may swap) @@ -51,6 +52,7 @@ struct kbuffer { unsigned int next; unsigned int size; unsigned int start; + unsigned int first; unsigned int (*read_4)(void *ptr); unsigned long long (*read_8)(void *ptr); @@ -546,6 +548,9 @@ int kbuffer_load_subbuffer(struct kbuffer *kbuf, void *subbuffer) next_event(kbuf); + /* save the first record from the page */ + kbuf->first = kbuf->curr; + return 0; } @@ -755,7 +760,7 @@ void kbuffer_set_old_format(struct kbuffer *kbuf) */ int kbuffer_start_of_data(struct kbuffer *kbuf) { - return kbuf->start; + return kbuf->first + kbuf->start; } /**