From 771fd155dfaa5332da69d606db16fe27bd9d388d Mon Sep 17 00:00:00 2001 From: Kan Liang Date: Thu, 19 Mar 2020 13:25:09 -0700 Subject: [PATCH] perf thread: Add a knob for LBR stitch approach The LBR stitch approach should be disabled by default. Because - The stitching approach base on LBR call stack technology. The known limitations of LBR call stack technology still apply to the approach, e.g. Exception handing such as setjmp/longjmp will have calls/returns not match. - This approach is not foolproof. There can be cases where it creates incorrect call stacks from incorrect matches. There is no attempt to validate any matches in another way. The 'lbr_stitch_enable' is used to indicate whether enable LBR stitch approach, which is disabled by default. The following patch will introduce a new option for each tools to enable the LBR stitch approach. Signed-off-by: Kan Liang Reviewed-by: Andi Kleen Acked-by: Jiri Olsa Cc: Adrian Hunter Cc: Alexey Budankov Cc: Mathieu Poirier Cc: Michael Ellerman Cc: Namhyung Kim Cc: Pavel Gerasimov Cc: Peter Zijlstra Cc: Ravi Bangoria Cc: Stephane Eranian Cc: Vitaly Slobodskoy Link: http://lore.kernel.org/lkml/20200319202517.23423-10-kan.liang@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/thread.c | 1 + tools/perf/util/thread.h | 3 +++ 2 files changed, 4 insertions(+) diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c index 28b719388028..1f080db23615 100644 --- a/tools/perf/util/thread.c +++ b/tools/perf/util/thread.c @@ -47,6 +47,7 @@ struct thread *thread__new(pid_t pid, pid_t tid) thread->tid = tid; thread->ppid = -1; thread->cpu = -1; + thread->lbr_stitch_enable = false; INIT_LIST_HEAD(&thread->namespaces_list); INIT_LIST_HEAD(&thread->comm_list); init_rwsem(&thread->namespaces_lock); diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h index 20b96b5d1f15..95294050cff2 100644 --- a/tools/perf/util/thread.h +++ b/tools/perf/util/thread.h @@ -46,6 +46,9 @@ struct thread { struct srccode_state srccode_state; bool filter; int filter_entry_depth; + + /* LBR call stack stitch */ + bool lbr_stitch_enable; }; struct machine;