lkml.org 
[lkml]   [2017]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] perf tools: Fix swap for samples with raw data
Em Wed, Nov 29, 2017 at 07:43:46PM +0100, Jiri Olsa escreveu:
> When we detect different endianity we swap event before
> processing. It's tricky for samples because we have no
> idea what's inside. We treat it as an array of u64s,
> swap them and later on we swap back parts which are
> different.

Thanks, applied to perf/core, now at:

https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=perf/core&id=26ea2ece7802f8fdaaacf321dbfb22de3271ab82

- Arnaldo

> We mangle this way also the tracepoint raw data, which
> ends up in report showing wrong data:
>
> 1.95% comm=Q^B pid=29285 prio=16777216 target_cpu=000
> 1.67% comm=l^B pid=0 prio=16777216 target_cpu=000
>
> Luckily the traceevent library handles the endianity by
> itself (thank you Steven!), so we can pass the RAW data
> directly in the other endianity.
>
> 2.51% comm=beah-rhts-task pid=1175 prio=120 target_cpu=002
> 2.23% comm=kworker/0:0 pid=11566 prio=120 target_cpu=000
>
> The fix is basically to swap back the raw data if different
> endianity is detected.
>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
> Link: http://lkml.kernel.org/n/tip-0zcnwqf2k4pq854huwxc1v4l@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> tools/perf/util/evsel.c | 20 +++++++++++++++++---
> 1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 95853c51c0ca..09c68cf2d9d2 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -36,6 +36,7 @@
> #include "debug.h"
> #include "trace-event.h"
> #include "stat.h"
> +#include "memswap.h"
> #include "util/parse-branch-options.h"
>
> #include "sane_ctype.h"
> @@ -2131,14 +2132,27 @@ int perf_evsel__parse_sample(struct perf_evsel *evsel, union perf_event *event,
> if (type & PERF_SAMPLE_RAW) {
> OVERFLOW_CHECK_u64(array);
> u.val64 = *array;
> - if (WARN_ONCE(swapped,
> - "Endianness of raw data not corrected!\n")) {
> - /* undo swap of u64, then swap on individual u32s */
> +
> + /*
> + * Undo swap of u64, then swap on individual u32s,
> + * get the size of the raw area and undo all of the
> + * swap. The pevent interface handles endianity by
> + * itself.
> + */
> + if (swapped) {
> u.val64 = bswap_64(u.val64);
> u.val32[0] = bswap_32(u.val32[0]);
> u.val32[1] = bswap_32(u.val32[1]);
> }
> data->raw_size = u.val32[0];
> +
> + /*
> + * The raw data is aligned on 64bits including the
> + * u32 size, so it's safe to use mem_bswap_64.
> + */
> + if (swapped)
> + mem_bswap_64((void *) array, data->raw_size);
> +
> array = (void *)array + sizeof(u32);
>
> OVERFLOW_CHECK(array, data->raw_size, max_size);
> --
> 2.13.6

\
 
 \ /
  Last update: 2017-12-11 21:09    [W:0.059 / U:0.700 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site