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perf core: Separate accounting of contexts and real addresses in a stack trace

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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>
This commit is contained in:
Arnaldo Carvalho de Melo
2016-05-12 13:06:21 -03:00
parent 3e4de4ec4c
commit c85b033496
5 changed files with 49 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
include/linux/perf_event.h
View File

@@ -65,6 +65,8 @@ struct perf_callchain_entry_ctx {
struct perf_callchain_entry *entry;
u32 max_stack;
u32 nr;
short contexts;
bool contexts_maxed;
};
struct perf_raw_record {
@@ -1078,12 +1080,24 @@ extern int get_callchain_buffers(void);
extern void put_callchain_buffers(void);
extern int sysctl_perf_event_max_stack;
extern int sysctl_perf_event_max_contexts_per_stack;
#define perf_callchain_store_context(ctx, context) perf_callchain_store(ctx, context)
static inline int perf_callchain_store_context(struct perf_callchain_entry_ctx *ctx, u64 ip)
{
if (ctx->contexts < sysctl_perf_event_max_contexts_per_stack) {
struct perf_callchain_entry *entry = ctx->entry;
entry->ip[entry->nr++] = ip;
++ctx->contexts;
return 0;
} else {
ctx->contexts_maxed = true;
return -1; /* no more room, stop walking the stack */
}
}
static inline int perf_callchain_store(struct perf_callchain_entry_ctx *ctx, u64 ip)
{
if (ctx->nr < ctx->max_stack) {
if (ctx->nr < ctx->max_stack && !ctx->contexts_maxed) {
struct perf_callchain_entry *entry = ctx->entry;
entry->ip[entry->nr++] = ip;
++ctx->nr;