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SubjectRe: [PATCH v1 2/3] perf session: Add swap operation for event TIME_CONV
Hi Adrian,

On Mon, Apr 26, 2021 at 08:40:00AM +0300, Adrian Hunter wrote:

[...]

> > +static void perf_event__time_conv_swap(union perf_event *event,
> > + bool sample_id_all __maybe_unused)
> > +{
> > + size_t time_zero_size;
> > +
> > + event->time_conv.time_shift = bswap_64(event->time_conv.time_shift);
> > + event->time_conv.time_mult = bswap_64(event->time_conv.time_mult);
> > + event->time_conv.time_zero = bswap_64(event->time_conv.time_zero);
> > +
> > + time_zero_size = (void *)&event->time_conv.time_cycles - (void *)event;
> > + if (event->header.size > time_zero_size) {
>
> I wonder if we could have a helper for this e.g. (untested)
>
> #define event_contains(obj, mem) (obj.header.size > offsetof(typeof(obj), mem))
>
> if (event_contains(event->time_conv, time_cycles)) {

Yeah, this is a better implementation. Will refine patch for this.

> > + event->time_conv.time_cycles = bswap_64(event->time_conv.time_cycles);
> > + event->time_conv.time_mask = bswap_64(event->time_conv.time_mask);
> > + event->time_conv.cap_user_time_zero =
> > + bswap_32(event->time_conv.cap_user_time_zero);
> > + event->time_conv.cap_user_time_short =
> > + bswap_32(event->time_conv.cap_user_time_short);
>
> 'struct perf_record_time_conv' contains bool, the sizeof which, AFAIK, is not defined.
> Is it really 4 bytes on your implementation? It is only 1 byte with gcc on x86.

On Arm64, bool is also 1 byte with GCC.

When working on this patch, I checked the size for structure
perf_record_time_conv, it gave out the structure size is 56; I wrongly
thought the bool size is 4 bytes and there have no padding. In fact,
bool size is 1 byte and GCC pads 6 bytes at the end of structure.

> Either way, you should change 'struct perf_record_time_conv' so it uses a type of known size.
> Since you are the only one using it, it should match your implementation.

Will change to "unsigned int" value. Thank you for reviewing and
suggestions.

Leo

> > + }
> > +}
> > +
> > typedef void (*perf_event__swap_op)(union perf_event *event,
> > bool sample_id_all);
> >
> > @@ -985,7 +1005,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
> > [PERF_RECORD_STAT] = perf_event__stat_swap,
> > [PERF_RECORD_STAT_ROUND] = perf_event__stat_round_swap,
> > [PERF_RECORD_EVENT_UPDATE] = perf_event__event_update_swap,
> > - [PERF_RECORD_TIME_CONV] = perf_event__all64_swap,
> > + [PERF_RECORD_TIME_CONV] = perf_event__time_conv_swap,
> > [PERF_RECORD_HEADER_MAX] = NULL,
> > };
> >
> >
>

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