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perf tools: Construct LBR call chain

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LBR call stack only has user-space callchains. It is output in the
PERF_SAMPLE_BRANCH_STACK data format. For kernel callchains, it's
still in the form of PERF_SAMPLE_CALLCHAIN.

The perf tool has to handle both data sources to construct a
complete callstack.

For the "perf report -D" option, both lbr and fp information will be
displayed.

A new call chain recording option "lbr" is introduced into the perf
tool for LBR call stack. The user can use --call-graph lbr to get
the call stack information from hardware.

Here are some examples.

When profiling bc(1) on Fedora 19:

  echo 'scale=2000; 4*a(1)' > cmd; perf record --call-graph lbr bc -l < cmd

If enabling LBR, perf report output looks like:

    50.36%       bc  bc                 [.] bc_divide
                 |
                 --- bc_divide
                     execute
                     run_code
                     yyparse
                     main
                     __libc_start_main
                     _start
    33.66%       bc  bc                 [.] _one_mult
                 |
                 --- _one_mult
                     bc_divide
                     execute
                     run_code
                     yyparse
                     main
                     __libc_start_main
                     _start
     7.62%       bc  bc                 [.] _bc_do_add
                 |
                 --- _bc_do_add
                    |
                    |--99.89%-- 0x2000186a8
                     --0.11%-- [...]
     6.83%       bc  bc                 [.] _bc_do_sub
                 |
                 --- _bc_do_sub
                    |
                    |--99.94%-- bc_add
                    |          execute
                    |          run_code
                    |          yyparse
                    |          main
                    |          __libc_start_main
                    |          _start
                     --0.06%-- [...]
     0.46%       bc  libc-2.17.so       [.] __memset_sse2
                 |
                 --- __memset_sse2
                    |
                    |--54.13%-- bc_new_num
                    |          |
                    |          |--51.00%-- bc_divide
                    |          |          execute
                    |          |          run_code
                    |          |          yyparse
                    |          |          main
                    |          |          __libc_start_main
                    |          |          _start
                    |          |
                    |          |--30.46%-- _bc_do_sub
                    |          |          bc_add
                    |          |          execute
                    |          |          run_code
                    |          |          yyparse
                    |          |          main
                    |          |          __libc_start_main
                    |          |          _start
                    |          |
                    |           --18.55%-- _bc_do_add
                    |                     bc_add
                    |                     execute
                    |                     run_code
                    |                     yyparse
                    |                     main
                    |                     __libc_start_main
                    |                     _start
                    |
                     --45.87%-- bc_divide
                               execute
                               run_code
                               yyparse
                               main
                               __libc_start_main
                               _start

If using FP, perf report output looks like:

  echo 'scale=2000; 4*a(1)' > cmd; perf record --call-graph fp bc -l < cmd

    50.49%       bc  bc                 [.] bc_divide
                 |
                 --- bc_divide
    33.57%       bc  bc                 [.] _one_mult
                 |
                 --- _one_mult
     7.61%       bc  bc                 [.] _bc_do_add
                 |
                 --- _bc_do_add
                     0x2000186a8
     6.88%       bc  bc                 [.] _bc_do_sub
                 |
                 --- _bc_do_sub
     0.42%       bc  libc-2.17.so       [.] __memcpy_ssse3_back
                 |
                 --- __memcpy_ssse3_back

If using LBR, perf report -D output looks like:

3458145275743 0x2fd750 [0xd8]: PERF_RECORD_SAMPLE(IP, 0x2): 9748/9748: 0x408ea8 period: 609644 addr: 0
... LBR call chain: nr:8
.....  0: fffffffffffffe00
.....  1: 0000000000408e50
.....  2: 000000000040a458
.....  3: 000000000040562e
.....  4: 0000000000408590
.....  5: 00000000004022c0
.....  6: 00000000004015dd
.....  7: 0000003d1cc21b43
... FP chain: nr:2
.....  0: fffffffffffffe00
.....  1: 0000000000408ea8
 ... thread: bc:9748
 ...... dso: /usr/bin/bc

The LBR call stack has the following known limitations:

 - Zero length calls are not filtered out by the hardware

 - Exception handing such as setjmp/longjmp will have calls/returns not
   match

 - Pushing different return address onto the stack will have
   calls/returns not match

 - If callstack is deeper than the LBR, only the last entries are
   captured

Tested-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Simon Que <sque@chromium.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1420482185-29830-3-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kan Liang 2015-01-05 13:23:05 -05:00 committed by Ingo Molnar
parent aad2b21c15
commit 384b60557b
3 changed files with 153 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
tools/perf/util/evsel.h
View File

@ -355,4 +355,8 @@ for ((_evsel) = list_entry((_leader)->node.next, struct perf_evsel, node); \
(_evsel) && (_evsel)->leader == (_leader); \
(_evsel) = list_entry((_evsel)->node.next, struct perf_evsel, node))
static inline bool has_branch_callstack(struct perf_evsel *evsel)
{
return evsel->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK;
}
#endif /* __PERF_EVSEL_H */

102
tools/perf/util/machine.c
View File

@ -1502,18 +1502,100 @@ static int remove_loops(struct branch_entry *l, int nr)
return nr;
}
static int thread__resolve_callchain_sample(struct thread *thread,
struct ip_callchain *chain,
struct branch_stack *branch,
struct symbol **parent,
struct addr_location *root_al,
int max_stack)
/*
* Recolve LBR callstack chain sample
* Return:
* 1 on success get LBR callchain information
* 0 no available LBR callchain information, should try fp
* negative error code on other errors.
*/
static int resolve_lbr_callchain_sample(struct thread *thread,
struct perf_sample *sample,
struct symbol **parent,
struct addr_location *root_al,
int max_stack)
{
struct ip_callchain *chain = sample->callchain;
int chain_nr = min(max_stack, (int)chain->nr);
int i, j, err;
u64 ip;
for (i = 0; i < chain_nr; i++) {
if (chain->ips[i] == PERF_CONTEXT_USER)
break;
}
/* LBR only affects the user callchain */
if (i != chain_nr) {
struct branch_stack *lbr_stack = sample->branch_stack;
int lbr_nr = lbr_stack->nr;
/*
* LBR callstack can only get user call chain.
* The mix_chain_nr is kernel call chain
* number plus LBR user call chain number.
* i is kernel call chain number,
* 1 is PERF_CONTEXT_USER,
* lbr_nr + 1 is the user call chain number.
* For details, please refer to the comments
* in callchain__printf
*/
int mix_chain_nr = i + 1 + lbr_nr + 1;
if (mix_chain_nr > PERF_MAX_STACK_DEPTH + PERF_MAX_BRANCH_DEPTH) {
pr_warning("corrupted callchain. skipping...\n");
return 0;
}
for (j = 0; j < mix_chain_nr; j++) {
if (callchain_param.order == ORDER_CALLEE) {
if (j < i + 1)
ip = chain->ips[j];
else if (j > i + 1)
ip = lbr_stack->entries[j - i - 2].from;
else
ip = lbr_stack->entries[0].to;
} else {
if (j < lbr_nr)
ip = lbr_stack->entries[lbr_nr - j - 1].from;
else if (j > lbr_nr)
ip = chain->ips[i + 1 - (j - lbr_nr)];
else
ip = lbr_stack->entries[0].to;
}
err = add_callchain_ip(thread, parent, root_al, false, ip);
if (err)
return (err < 0) ? err : 0;
}
return 1;
}
return 0;
}
static int thread__resolve_callchain_sample(struct thread *thread,
struct perf_evsel *evsel,
struct perf_sample *sample,
struct symbol **parent,
struct addr_location *root_al,
int max_stack)
{
struct branch_stack *branch = sample->branch_stack;
struct ip_callchain *chain = sample->callchain;
int chain_nr = min(max_stack, (int)chain->nr);
int i, j, err;
int skip_idx = -1;
int first_call = 0;
callchain_cursor_reset(&callchain_cursor);
if (has_branch_callstack(evsel)) {
err = resolve_lbr_callchain_sample(thread, sample, parent,
root_al, max_stack);
if (err)
return (err < 0) ? err : 0;
}
/*
* Based on DWARF debug information, some architectures skip
* a callchain entry saved by the kernel.
@ -1521,8 +1603,6 @@ static int thread__resolve_callchain_sample(struct thread *thread,
if (chain->nr < PERF_MAX_STACK_DEPTH)
skip_idx = arch_skip_callchain_idx(thread, chain);
callchain_cursor_reset(&callchain_cursor);
/*
* Add branches to call stack for easier browsing. This gives
* more context for a sample than just the callers.
@ -1623,9 +1703,9 @@ int thread__resolve_callchain(struct thread *thread,
struct addr_location *root_al,
int max_stack)
{
int ret = thread__resolve_callchain_sample(thread, sample->callchain,
sample->branch_stack,
parent, root_al, max_stack);
int ret = thread__resolve_callchain_sample(thread, evsel,
sample, parent,
root_al, max_stack);
if (ret)
return ret;

64
tools/perf/util/session.c
View File

@ -553,15 +553,67 @@ int perf_session_queue_event(struct perf_session *s, union perf_event *event,
return 0;
}
static void callchain__printf(struct perf_sample *sample)
static void callchain__lbr_callstack_printf(struct perf_sample *sample)
{
struct ip_callchain *callchain = sample->callchain;
struct branch_stack *lbr_stack = sample->branch_stack;
u64 kernel_callchain_nr = callchain->nr;
unsigned int i;
printf("... chain: nr:%" PRIu64 "\n", sample->callchain->nr);
for (i = 0; i < kernel_callchain_nr; i++) {
if (callchain->ips[i] == PERF_CONTEXT_USER)
break;
}
if ((i != kernel_callchain_nr) && lbr_stack->nr) {
u64 total_nr;
/*
* LBR callstack can only get user call chain,
* i is kernel call chain number,
* 1 is PERF_CONTEXT_USER.
*
* The user call chain is stored in LBR registers.
* LBR are pair registers. The caller is stored
* in "from" register, while the callee is stored
* in "to" register.
* For example, there is a call stack
* "A"->"B"->"C"->"D".
* The LBR registers will recorde like
* "C"->"D", "B"->"C", "A"->"B".
* So only the first "to" register and all "from"
* registers are needed to construct the whole stack.
*/
total_nr = i + 1 + lbr_stack->nr + 1;
kernel_callchain_nr = i + 1;
printf("... LBR call chain: nr:%" PRIu64 "\n", total_nr);
for (i = 0; i < kernel_callchain_nr; i++)
printf("..... %2d: %016" PRIx64 "\n",
i, callchain->ips[i]);
for (i = 0; i < sample->callchain->nr; i++)
printf("..... %2d: %016" PRIx64 "\n",
i, sample->callchain->ips[i]);
(int)(kernel_callchain_nr), lbr_stack->entries[0].to);
for (i = 0; i < lbr_stack->nr; i++)
printf("..... %2d: %016" PRIx64 "\n",
(int)(i + kernel_callchain_nr + 1), lbr_stack->entries[i].from);
}
}
static void callchain__printf(struct perf_evsel *evsel,
struct perf_sample *sample)
{
unsigned int i;
struct ip_callchain *callchain = sample->callchain;
if (has_branch_callstack(evsel))
callchain__lbr_callstack_printf(sample);
printf("... FP chain: nr:%" PRIu64 "\n", callchain->nr);
for (i = 0; i < callchain->nr; i++)
printf("..... %2d: %016" PRIx64 "\n",
i, callchain->ips[i]);
}
static void branch_stack__printf(struct perf_sample *sample)
@ -718,9 +770,9 @@ static void dump_sample(struct perf_evsel *evsel, union perf_event *event,
sample_type = evsel->attr.sample_type;
if (sample_type & PERF_SAMPLE_CALLCHAIN)
callchain__printf(sample);
callchain__printf(evsel, sample);
if (sample_type & PERF_SAMPLE_BRANCH_STACK)
if ((sample_type & PERF_SAMPLE_BRANCH_STACK) && !has_branch_callstack(evsel))
branch_stack__printf(sample);
if (sample_type & PERF_SAMPLE_REGS_USER)