From b4b046ff9e3410593db7b35326cf696810af8f4f Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Thu, 1 Jul 2021 20:51:32 +0300 Subject: perf intel-pt: Add a config for max loops without consuming a packet The Intel PT decoder limits the number of unconditional branches (e.g. jmps) decoded without consuming any trace packets. Generally, a loop needs a conditional branch which generates a TNT packet, whereas a "ret" instruction will generate a TIP or TNT packet. So exceeding the limit is assumed to be a never-ending loop, which can happen if there has been a decoding error putting the decoder at the wrong place in the code. Up until now, the limit of 10000 has been enough but some analytic purposes have been reported to exceed that. Increase the limit to 100000, and make it configurable via perf config intel-pt.max-loops. Also amend the "Never-ending loop" message to mention the configuration entry. Signed-off-by: Adrian Hunter Reviewed-by: Andi Kleen Cc: Jiri Olsa Link: http://lore.kernel.org/lkml/20210701175132.3977-1-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/Documentation/perf-config.txt | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'tools/perf/Documentation') diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt index b0872c801866..3bb75c1f25e8 100644 --- a/tools/perf/Documentation/perf-config.txt +++ b/tools/perf/Documentation/perf-config.txt @@ -706,6 +706,12 @@ intel-pt.*:: If set, Intel PT decoder will set the mispred flag on all branches. + intel-pt.max-loops:: + If set and non-zero, the maximum number of unconditional + branches decoded without consuming any trace packets. If + the maximum is exceeded there will be a "Never-ending loop" + error. The default is 100000. + auxtrace.*:: auxtrace.dumpdir:: -- cgit v1.2.3