Re: [PATCH 1/2] perf tools: Fix sample size bit operations

Ingo Molnar
2011-05-23T11:28:27Z

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> What we want is to count the number of bits in the mask,
> not some other random operation written in the middle
> of the night.
>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Stephane Eranian <eranian@google.com>
> ---
> tools/perf/util/event.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 17c1c3c..d3fa7e4 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -42,7 +42,7 @@ int perf_sample_size(u64 sample_type)
> int i;
>
> for (i = 0; i < 64; i++) {
> - if ((mask << i) & 1)
> + if (mask & (1 << i))
> size++;
> }

I fixed this to be 1UL and applied your fixes out of email - perf top and perf
report works fine now, so this was a 64-bitness bug (you probably used a 32-bit
system for testing?).

Btw., shouldnt this use hweight() or such?

Thanks,

Ingo