Messages in this thread | | | Date | Tue, 6 Jul 2021 16:15:39 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf script python: Fix buffer size to report iregs in perf script |
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Em Tue, Jul 06, 2021 at 05:26:12PM +0530, kajoljain escreveu: > > > On 6/29/21 12:39 PM, kajoljain wrote: > > > > > > On 6/28/21 8:19 PM, Paul A. Clarke wrote: > >> On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote: > >>> Commit 48a1f565261d ("perf script python: Add more PMU fields > >>> to event handler dict") added functionality to report fields like > >>> weight, iregs, uregs etc via perf report. > >>> That commit predefined buffer size to 512 bytes to print those fields. > >>> > >>> But incase of powerpc, since we added extended regs support > >>> in commits: > >>> > >>> Commit 068aeea3773a ("perf powerpc: Support exposing Performance Monitor > >>> Counter SPRs as part of extended regs") > >>> Commit d735599a069f ("powerpc/perf: Add extended regs support for > >>> power10 platform") > >>> > >>> Now iregs can carry more bytes of data and this predefined buffer size > >>> can result to data loss in perf script output. > >>> > >>> Patch resolve this issue by making buffer size dynamic based on number > >>> of registers needed to print. It also changed return type for function > >>> "regs_map" from int to void, as the return value is not being used by > >>> the caller function "set_regs_in_dict". > >>> > >>> Fixes: 068aeea3773a ("perf powerpc: Support exposing Performance Monitor > >>> Counter SPRs as part of extended regs") > >>> Signed-off-by: Kajol Jain <kjain@linux.ibm.com> > >>> --- > >>> .../util/scripting-engines/trace-event-python.c | 17 ++++++++++++----- > >>> 1 file changed, 12 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c > >>> index 4e4aa4c97ac5..c8c9706b4643 100644 > >>> --- a/tools/perf/util/scripting-engines/trace-event-python.c > >>> +++ b/tools/perf/util/scripting-engines/trace-event-python.c > >> [...] > >>> @@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict, > >>> struct evsel *evsel) > >>> { > >>> struct perf_event_attr *attr = &evsel->core.attr; > >>> - char bf[512]; > >>> + > >>> + /* > >>> + * Here value 28 is a constant size which can be used to print > >>> + * one register value and its corresponds to: > >>> + * 16 chars is to specify 64 bit register in hexadecimal. > >>> + * 2 chars is for appending "0x" to the hexadecimal value and > >>> + * 10 chars is for register name. > >>> + */ > >>> + int size = __sw_hweight64(attr->sample_regs_intr) * 28; > >>> + char bf[size]; > >> > >> I propose using a template rather than a magic number here. Something like: > >> const char reg_name_tmpl[] = "10 chars "; > >> const char reg_value_tmpl[] = "0x0123456789abcdef"; > >> const int size = __sw_hweight64(attr->sample_regs_intr) + > >> sizeof reg_name_tmpl + sizeof reg_value_tmpl; > >> > > > > Hi Paul, > > Thanks for reviewing the patch. Yes these are > > some standardization we can do by creating macros for different > > fields. > > The basic idea is, we want to provide significant buffer size > > based on number of registers present in sample_regs_intr to accommodate > > all data. > > > > Hi Arnaldo/Jiri, > Is the approach used in this patch looks fine to you?
Yeah, and the comment you provide right above it explains it, so I think that is enough, ok?
- Arnaldo
> Thanks, > Kajol Jain > > > But before going to optimizing code, Arnaldo/Jiri, is this approach looks good to you? > > > >> Pardon my ignorance, but is there no separation/whitespace between the name > >> and the value? > > > > This is how we will get data via perf script > > > > r0:0xc000000000112008 > > r1:0xc000000023b37920 > > r2:0xc00000000144c900 > > r3:0xc0000000bc566120 > > r4:0xc0000000c5600000 > > r5:0x2606c6506ca > > r6:0xc000000023b378f8 > > r7:0xfffffd9f93a48f0e > > ..... > > > > And is there some significance to 10 characters for the > >> register name, or is that a magic number? > > > > Most of the register name are within 10 characters, basically we are giving this > > magic number to make sure we have enough space in buffer to contain all registers > > name with colon. > > > > Thanks, > > Kajol Jain > > > >> > >> PC > >>
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- Arnaldo
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