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perf core: Add a 'nr' field to perf_event_callchain_context

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We will use it to count how many addresses are in the entry->ip[] array,
excluding PERF_CONTEXT_{KERNEL,USER,etc} entries, so that we can really
return the number of entries specified by the user via the relevant
sysctl, kernel.perf_event_max_contexts, or via the per event
perf_event_attr.sample_max_stack knob.

This way we keep the perf_sample->ip_callchain->nr meaning, that is the
number of entries, be it real addresses or PERF_CONTEXT_ entries, while
honouring the max_stack knobs, i.e. the end result will be max_stack
entries if we have at least that many entries in a given stack trace.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-s8teto51tdqvlfhefndtat9r@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo
2016-05-10 18:08:32 -03:00
parent cfbcf46845
commit 3b1fff0803
9 changed files with 18 additions and 17 deletions
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6
include/linux/perf_event.h
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@@ -64,6 +64,7 @@ struct perf_callchain_entry {
struct perf_callchain_entry_ctx {
struct perf_callchain_entry *entry;
u32 max_stack;
u32 nr;
};
struct perf_raw_record {
@@ -1080,9 +1081,10 @@ extern int sysctl_perf_event_max_stack;
static inline int perf_callchain_store(struct perf_callchain_entry_ctx *ctx, u64 ip)
{
struct perf_callchain_entry *entry = ctx->entry;
if (entry->nr < ctx->max_stack) {
if (ctx->nr < ctx->max_stack) {
struct perf_callchain_entry *entry = ctx->entry;
entry->ip[entry->nr++] = ip;
++ctx->nr;
return 0;
} else {
return -1; /* no more room, stop walking the stack */