[RFC 1/1] perf tools/kernel: Per event max-stack settings

From: Arnaldo Carvalho de Melo
Date: Tue May 17 2016 - 11:41:18 EST

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Hi,

So I have the patch below + the kernel code to handle it, i.e. per-event
max-stack, in addition to the system wide kernel.perf_event_max_stack
knob.

Interested people should try my perf/max-stack branch, where the two
patches to implement this are at the top:

https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/log/?h=perf/max-stack

But people have expressed interested in being able to have kernel/user
separate max-stack knobs, which should be easy to do with the way things
are laid out now (that perf_callchain_entry_ctx thing).

One way would be to use a one bit flag sample_max_stack_split and then a
union to split perf_event_attr.sample_max_stack in two u16, that way we
wouldn't extend the perf_event_attr size, but then we wouldn't be able
to have both per event limits for the kernel+user stack and separate
max-stack limits for for kernel and user, is that an acceptable
limitation?

I couldn't find other members I could put in a union where to store the
sample_max_stack_{user,kernel} values, ideas?

I think that we should push what I have there anyway, the split would
come later, be it by using:

__u64 sample_max_stack_split:1;
__u64 __reserved_1:35;
<SNIP>
union {
__u32 sample_max_stack;
struct {
__u16 sample_max_stack_user;
__u16 sample_max_stack_kernel;
};
};

Or by having space for all three.

- Arnaldo

-------------------------------------------------------------------------------------

The tooling counterpart, now it is possible to do have some events using
"fp" stacks traces, while others use 'dwarf' or something else with all
of them having different max-stack settings, as needed:

# perf record -e sched:sched_switch/max-stack=10/ -e cycles/call-graph=dwarf,max-stack=4/ -e cpu-cycles/call-graph=dwarf,max-stack=1024/ usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.052 MB perf.data (5 samples) ]
# perf evlist -v
sched:sched_switch: type: 2, size: 112, config: 0x110, { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CALLCHAIN|CPU|PERIOD|RAW|IDENTIFIER, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, sample_max_stack: 10
cycles/call-graph=dwarf,max-stack=4/: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CALLCHAIN|PERIOD|REGS_USER|STACK_USER|IDENTIFIER, read_format: ID, disabled: 1, inherit: 1, freq: 1, enable_on_exec: 1, sample_id_all: 1, exclude_guest: 1, exclude_callchain_user: 1, sample_regs_user: 0xff0fff, sample_stack_user: 8192, sample_max_stack: 4
cpu-cycles/call-graph=dwarf,max-stack=1024/: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CALLCHAIN|PERIOD|REGS_USER|STACK_USER|IDENTIFIER, read_format: ID, disabled: 1, inherit: 1, freq: 1, enable_on_exec: 1, sample_id_all: 1, exclude_guest: 1, exclude_callchain_user: 1, sample_regs_user: 0xff0fff, sample_stack_user: 8192, sample_max_stack: 1024
# Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events

Using just /max-stack=N/ means /call-graph=fp,max-stack=N/, that should
be further configurable by means of some .perfconfig knob.

Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/util/callchain.h | 1 +
tools/perf/util/evsel.c | 16 ++++++++++++++--
tools/perf/util/evsel.h | 2 ++
tools/perf/util/parse-events.c | 8 ++++++++
tools/perf/util/parse-events.h | 1 +
tools/perf/util/parse-events.l | 1 +
tools/perf/util/session.c | 1 +
7 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
index 65e2a4f7cb4e..9101dbed4ac3 100644
--- a/tools/perf/util/callchain.h
+++ b/tools/perf/util/callchain.h
@@ -95,6 +95,7 @@ struct callchain_param {
u32 dump_size;
enum chain_mode mode;
u32 print_limit;
+ u32 max_stack;
double min_percent;
sort_chain_func_t sort;
enum chain_order order;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index a23f54793e51..9f3871185550 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -571,6 +571,8 @@ void perf_evsel__config_callchain(struct perf_evsel *evsel,

perf_evsel__set_sample_bit(evsel, CALLCHAIN);

+ attr->sample_max_stack = param->max_stack;
+
if (param->record_mode == CALLCHAIN_LBR) {
if (!opts->branch_stack) {
if (attr->exclude_user) {
@@ -634,7 +636,8 @@ static void apply_config_terms(struct perf_evsel *evsel,
struct perf_event_attr *attr = &evsel->attr;
struct callchain_param param;
u32 dump_size = 0;
- char *callgraph_buf = NULL;
+ u32 max_stack = 0;
+ const char *callgraph_buf = NULL;

/* callgraph default */
param.record_mode = callchain_param.record_mode;
@@ -661,6 +664,9 @@ static void apply_config_terms(struct perf_evsel *evsel,
case PERF_EVSEL__CONFIG_TERM_STACK_USER:
dump_size = term->val.stack_user;
break;
+ case PERF_EVSEL__CONFIG_TERM_MAX_STACK:
+ max_stack = term->val.max_stack;
+ break;
case PERF_EVSEL__CONFIG_TERM_INHERIT:
/*
* attr->inherit should has already been set by
@@ -676,7 +682,12 @@ static void apply_config_terms(struct perf_evsel *evsel,
}

/* User explicitly set per-event callgraph, clear the old setting and reset. */
- if ((callgraph_buf != NULL) || (dump_size > 0)) {
+ if ((callgraph_buf != NULL) || (dump_size > 0) || max_stack) {
+ if (max_stack) {
+ param.max_stack = max_stack;
+ if (callgraph_buf == NULL)
+ callgraph_buf = "fp";
+ }

/* parse callgraph parameters */
if (callgraph_buf != NULL) {
@@ -1328,6 +1339,7 @@ int perf_event_attr__fprintf(FILE *fp, struct perf_event_attr *attr,
PRINT_ATTRf(clockid, p_signed);
PRINT_ATTRf(sample_regs_intr, p_hex);
PRINT_ATTRf(aux_watermark, p_unsigned);
+ PRINT_ATTRf(sample_max_stack, p_unsigned);

return ret;
}
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 8a644fef452c..caaab94aea95 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -44,6 +44,7 @@ enum {
PERF_EVSEL__CONFIG_TERM_CALLGRAPH,
PERF_EVSEL__CONFIG_TERM_STACK_USER,
PERF_EVSEL__CONFIG_TERM_INHERIT,
+ PERF_EVSEL__CONFIG_TERM_MAX_STACK,
PERF_EVSEL__CONFIG_TERM_MAX,
};

@@ -56,6 +57,7 @@ struct perf_evsel_config_term {
bool time;
char *callgraph;
u64 stack_user;
+ u32 max_stack;
bool inherit;
} val;
};
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index bcbc983d4b12..89d40bb425e1 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -900,6 +900,7 @@ static const char *config_term_names[__PARSE_EVENTS__TERM_TYPE_NR] = {
[PARSE_EVENTS__TERM_TYPE_STACKSIZE] = "stack-size",
[PARSE_EVENTS__TERM_TYPE_NOINHERIT] = "no-inherit",
[PARSE_EVENTS__TERM_TYPE_INHERIT] = "inherit",
+ [PARSE_EVENTS__TERM_TYPE_MAX_STACK] = "max-stack",
};

static bool config_term_shrinked;
@@ -995,6 +996,9 @@ do { \
case PARSE_EVENTS__TERM_TYPE_NAME:
CHECK_TYPE_VAL(STR);
break;
+ case PARSE_EVENTS__TERM_TYPE_MAX_STACK:
+ CHECK_TYPE_VAL(NUM);
+ break;
default:
err->str = strdup("unknown term");
err->idx = term->err_term;
@@ -1040,6 +1044,7 @@ static int config_term_tracepoint(struct perf_event_attr *attr,
case PARSE_EVENTS__TERM_TYPE_STACKSIZE:
case PARSE_EVENTS__TERM_TYPE_INHERIT:
case PARSE_EVENTS__TERM_TYPE_NOINHERIT:
+ case PARSE_EVENTS__TERM_TYPE_MAX_STACK:
return config_term_common(attr, term, err);
default:
if (err) {
@@ -1109,6 +1114,9 @@ do { \
case PARSE_EVENTS__TERM_TYPE_NOINHERIT:
ADD_CONFIG_TERM(INHERIT, inherit, term->val.num ? 0 : 1);
break;
+ case PARSE_EVENTS__TERM_TYPE_MAX_STACK:
+ ADD_CONFIG_TERM(MAX_STACK, max_stack, term->val.num);
+ break;
default:
break;
}
diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index d740c3ca9a1d..46c05ccd5dfe 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -68,6 +68,7 @@ enum {
PARSE_EVENTS__TERM_TYPE_STACKSIZE,
PARSE_EVENTS__TERM_TYPE_NOINHERIT,
PARSE_EVENTS__TERM_TYPE_INHERIT,
+ PARSE_EVENTS__TERM_TYPE_MAX_STACK,
__PARSE_EVENTS__TERM_TYPE_NR,
};

diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 1477fbc78993..01af1ee90a27 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -199,6 +199,7 @@ branch_type { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_BRANCH_SAMPLE_TYPE
time { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_TIME); }
call-graph { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_CALLGRAPH); }
stack-size { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_STACKSIZE); }
+max-stack { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_MAX_STACK); }
inherit { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_INHERIT); }
no-inherit { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_NOINHERIT); }
, { return ','; }
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 2335b2824d8a..802c4ef5a47c 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -608,6 +608,7 @@ do { \
bswap_field_64(sample_regs_user);
bswap_field_32(sample_stack_user);
bswap_field_32(aux_watermark);
+ bswap_field_32(sample_max_stack);

/*
* After read_format are bitfields. Check read_format because
--
2.5.5

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