From 151772dbfad4dbe81721e40f9b3d588ea77bb7aa Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Wed, 25 Aug 2010 11:32:38 +1000 Subject: [PATCH 1/3] tracing/trace_stack: Fix stack trace on ppc64 save_stack_trace() stores the instruction pointer, not the function descriptor. On ppc64 the trace stack code currently dereferences the instruction pointer and shows 8 bytes of instructions in our backtraces: # cat /sys/kernel/debug/tracing/stack_trace Depth Size Location (26 entries) ----- ---- -------- 0) 5424 112 0x6000000048000004 1) 5312 160 0x60000000ebad01b0 2) 5152 160 0x2c23000041c20030 3) 4992 240 0x600000007c781b79 4) 4752 160 0xe84100284800000c 5) 4592 192 0x600000002fa30000 6) 4400 256 0x7f1800347b7407e0 7) 4144 208 0xe89f0108f87f0070 8) 3936 272 0xe84100282fa30000 Since we aren't dealing with function descriptors, use %pS instead of %pF to fix it: # cat /sys/kernel/debug/tracing/stack_trace Depth Size Location (26 entries) ----- ---- -------- 0) 5424 112 ftrace_call+0x4/0x8 1) 5312 160 .current_io_context+0x28/0x74 2) 5152 160 .get_io_context+0x48/0xa0 3) 4992 240 .cfq_set_request+0x94/0x4c4 4) 4752 160 .elv_set_request+0x60/0x84 5) 4592 192 .get_request+0x2d4/0x468 6) 4400 256 .get_request_wait+0x7c/0x258 7) 4144 208 .__make_request+0x49c/0x610 8) 3936 272 .generic_make_request+0x390/0x434 Signed-off-by: Anton Blanchard Cc: rostedt@goodmis.org Cc: fweisbec@gmail.com LKML-Reference: <20100825013238.GE28360@kryten> Signed-off-by: Ingo Molnar --- kernel/trace/trace_stack.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index 056468eae7cf..a6b7e0e0f3eb 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -249,7 +249,7 @@ static int trace_lookup_stack(struct seq_file *m, long i) { unsigned long addr = stack_dump_trace[i]; - return seq_printf(m, "%pF\n", (void *)addr); + return seq_printf(m, "%pS\n", (void *)addr); } static void print_disabled(struct seq_file *m) From 8d330919927ea31fa083b5a80084dc991da813a0 Mon Sep 17 00:00:00 2001 From: Lin Ming Date: Wed, 25 Aug 2010 21:06:32 +0000 Subject: [PATCH 2/3] perf, x86, Pentium4: Clear the P4_CCCR_FORCE_OVF flag If on Pentium4 CPUs the FORCE_OVF flag is set then an NMI happens on every event, which can generate a flood of NMIs. Clear it. Reported-by: Vince Weaver Signed-off-by: Lin Ming Signed-off-by: Cyrill Gorcunov Cc: Frederic Weisbecker Cc: Peter Zijlstra Cc: Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_p4.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c index febb12cea795..7e578e9cc58b 100644 --- a/arch/x86/kernel/cpu/perf_event_p4.c +++ b/arch/x86/kernel/cpu/perf_event_p4.c @@ -497,6 +497,8 @@ static int p4_hw_config(struct perf_event *event) event->hw.config |= event->attr.config & (p4_config_pack_escr(P4_ESCR_MASK_HT) | p4_config_pack_cccr(P4_CCCR_MASK_HT | P4_CCCR_RESERVED)); + + event->hw.config &= ~P4_CCCR_FORCE_OVF; } rc = x86_setup_perfctr(event); From 5225c45899e872383ca39f5533d28ec63c54b39e Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 22 Aug 2010 04:29:17 +0200 Subject: [PATCH 3/3] perf: Initialize callchains roots's childen hits Each histogram entry has a callchain root that stores the callchain samples. However we forgot to initialize the tracking of children hits of these roots, which then got random values on their creation. The root children hits is multiplied by the minimum percentage of hits provided by the user, and the result becomes the minimum hits expected from children branches. If the random value due to the uninitialization is big enough, then this minimum number of hits can be huge and eventually filter every children branches. The end result was invisible callchains. All we need to fix this is to initialize the children hits of the root. Reported-by: Christoph Hellwig Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras Cc: 2.6.32.x-2.6.35.y --- tools/perf/util/callchain.h | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h index 624a96c636fd..6de4313924fb 100644 --- a/tools/perf/util/callchain.h +++ b/tools/perf/util/callchain.h @@ -50,6 +50,7 @@ static inline void callchain_init(struct callchain_node *node) INIT_LIST_HEAD(&node->children); INIT_LIST_HEAD(&node->val); + node->children_hit = 0; node->parent = NULL; node->hit = 0; }