perf core: Separate accounting of contexts and real addresses in a stack trace
The perf_sample->ip_callchain->nr value includes all the entries in the
ip_callchain->ip[] array, real addresses and PERF_CONTEXT_{KERNEL,USER,etc},
while what the user expects is that what is in the kernel.perf_event_max_stack
sysctl or in the upcoming per event perf_event_attr.sample_max_stack knob be
honoured in terms of IP addresses in the stack trace.
So allocate a bunch of extra entries for contexts, and do the accounting
via perf_callchain_entry_ctx struct members.
A new sysctl, kernel.perf_event_max_contexts_per_stack is also
introduced for investigating possible bugs in the callchain
implementation by some arch.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/n/tip-3b4wnqk340c4sg4gwkfdi9yk@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index ca64573..179ef46 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -19,11 +19,13 @@
};
int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
+int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK;
static inline size_t perf_callchain_entry__sizeof(void)
{
return (sizeof(struct perf_callchain_entry) +
- sizeof(__u64) * sysctl_perf_event_max_stack);
+ sizeof(__u64) * (sysctl_perf_event_max_stack +
+ sysctl_perf_event_max_contexts_per_stack));
}
static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
@@ -197,6 +199,8 @@
ctx.entry = entry;
ctx.max_stack = max_stack;
ctx.nr = entry->nr = init_nr;
+ ctx.contexts = 0;
+ ctx.contexts_maxed = false;
if (kernel && !user_mode(regs)) {
if (add_mark)
@@ -228,6 +232,10 @@
return entry;
}
+/*
+ * Used for sysctl_perf_event_max_stack and
+ * sysctl_perf_event_max_contexts_per_stack.
+ */
int perf_event_max_stack_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 0ec6907..bec4c11 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1156,6 +1156,15 @@
.extra1 = &zero,
.extra2 = &six_hundred_forty_kb,
},
+ {
+ .procname = "perf_event_max_contexts_per_stack",
+ .data = &sysctl_perf_event_max_contexts_per_stack,
+ .maxlen = sizeof(sysctl_perf_event_max_contexts_per_stack),
+ .mode = 0644,
+ .proc_handler = perf_event_max_stack_handler,
+ .extra1 = &zero,
+ .extra2 = &one_thousand,
+ },
#endif
#ifdef CONFIG_KMEMCHECK
{