Messages in this thread | | | From | "Hunter, Adrian" <> | Subject | RE: [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode | Date | Tue, 13 Jul 2021 17:31:03 +0000 |
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> -----Original Message----- > From: Leo Yan <leo.yan@linaro.org> > Sent: Tuesday, July 13, 2021 6:10 PM > To: Arnaldo Carvalho de Melo <acme@kernel.org> > Cc: Hunter, Adrian <adrian.hunter@intel.com>; Peter Zijlstra > <peterz@infradead.org>; Ingo Molnar <mingo@redhat.com>; Mark Rutland > <mark.rutland@arm.com>; Alexander Shishkin > <alexander.shishkin@linux.intel.com>; Jiri Olsa <jolsa@redhat.com>; > Namhyung Kim <namhyung@kernel.org>; Thomas Gleixner > <tglx@linutronix.de>; Borislav Petkov <bp@alien8.de>; x86@kernel.org; H. > Peter Anvin <hpa@zytor.com>; Mathieu Poirier > <mathieu.poirier@linaro.org>; Suzuki K Poulose > <suzuki.poulose@arm.com>; Mike Leach <mike.leach@linaro.org>; linux- > perf-users@vger.kernel.org; linux-kernel@vger.kernel.org; > coresight@lists.linaro.org; linux-arm-kernel@lists.infradead.org > Subject: Re: [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode > > Hi Arnaldo, Adrian, > > On Mon, Jul 12, 2021 at 03:14:35PM -0300, Arnaldo Carvalho de Melo wrote: > > Em Sun, Jul 11, 2021 at 06:41:04PM +0800, Leo Yan escreveu: > > > It's useful to know that the kernel is running in 32-bit or 64-bit > > > mode. E.g. We can decide if perf tool is running in compat mode > > > from this info. > > > > > > This patch adds a global variable "kernel_is_64_bit", it's > > > initialized when a session setups environment, its value is decided > > > by checking the architecture string. > > > > > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > > > --- > > > tools/perf/util/env.c | 17 ++++++++++++++++- tools/perf/util/env.h > > > | 1 + > > > 2 files changed, 17 insertions(+), 1 deletion(-) > > > > > > diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c index > > > ebc5e9ad35db..345635a2e842 100644 > > > --- a/tools/perf/util/env.c > > > +++ b/tools/perf/util/env.c > > > @@ -11,6 +11,7 @@ > > > #include <stdlib.h> > > > #include <string.h> > > > > > > +int kernel_is_64_bit; > > > struct perf_env perf_env; > > > > Why can't this be in 'struct perf_env'? > > Good question. I considered to add it in struct perf_env but finally I used this > way; the reason is this variable "kernel_is_64_bit" is only used during > recording phase for AUX ring buffer, and don't use it for report. So seems to > me it's over complexity to add a new field and just wander if it's necessary to > save this field as new feature in the perf header.
I think we store the arch, so if the "kernel_is_64_bit" calculation depends only on arch then I guess we don't need a new feature at the moment.
> > Combining the comment from Adrian in another email, I think it's good to add > a new field "compat_mode" in the struct perf_env, and this field will be > initialized in build-record.c. Currently we don't need to save this value into > the perf file, if later we need to use this value for decoding phase, then we > can add a new feature item to save "compat_mode" > into the perf file's header. > > If you have any different idea, please let me know. Thanks! > > Leo
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