[PATCH v3 11/13] perf report: cache srclines for callchain nodes

Milian Wolff
2017-09-06T13:55:42Z

On one hand this ensures that the memory is properly freed when
the DSO gets freed. On the other hand this significantly speeds up
the processing of the callchain nodes when lots of srclines are
requested. For one of my data files e.g.:

Before:

Performance counter stats for 'perf report -s srcline -g srcline --stdio':

52496.495043 task-clock (msec) # 0.999 CPUs utilized
634 context-switches # 0.012 K/sec
2 cpu-migrations # 0.000 K/sec
191,561 page-faults # 0.004 M/sec
165,074,498,235 cycles # 3.144 GHz
334,170,832,408 instructions # 2.02 insn per cycle
90,220,029,745 branches # 1718.591 M/sec
654,525,177 branch-misses # 0.73% of all branches

52.533273822 seconds time elapsedProcessed 236605 events and lost 40 chunks!

After:

Performance counter stats for 'perf report -s srcline -g srcline --stdio':

22606.323706 task-clock (msec) # 1.000 CPUs utilized
31 context-switches # 0.001 K/sec
0 cpu-migrations # 0.000 K/sec
185,471 page-faults # 0.008 M/sec
71,188,113,681 cycles # 3.149 GHz
133,204,943,083 instructions # 1.87 insn per cycle
34,886,384,979 branches # 1543.214 M/sec
278,214,495 branch-misses # 0.80% of all branches

22.609857253 seconds time elapsed

Note that the difference is only this large when `--inline` is not
passed. In such situations, we would use the inliner cache and
thus do not run this code path that often.

I think that this cache should actually be used in other places, too.
When looking at the valgrind leak report for perf report, we see tons
of srclines being leaked, most notably from calls to
hist_entry__get_srcline. The problem is that get_srcline has many
different formatting options (show_sym, show_addr, potentially even
unwind_inlines when calling __get_srcline directly). As such, the
srcline cannot easily be cached for all calls, or we'd have to add
caches for all formatting combinations (6 so far). An alternative
would be to remove the formatting options and handle that on a
different level - i.e. print the sym/addr on demand wherever we
actually output something. And the unwind_inlines could be moved into
a separate function that does not return the srcline.

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yao Jin <yao.jin@linux.intel.com>
Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
---
tools/perf/util/dso.c | 1 +
tools/perf/util/dso.h | 1 +
tools/perf/util/machine.c | 17 +++++++++---
tools/perf/util/srcline.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/srcline.h | 7 +++++
5 files changed, 89 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 72e6e390fd26..8c7f2862cff2 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1235,6 +1235,7 @@ void dso__delete(struct dso *dso)
for (i = 0; i < MAP__NR_TYPES; ++i)
symbols__delete(&dso->symbols[i]);
inlines__tree_delete(&dso->inlined_nodes);
+ srcline__tree_delete(&dso->srclines);

if (dso->short_name_allocated) {
zfree((char **)&dso->short_name);
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 7d1e2b3c1f10..ac3a65a30ff2 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -142,6 +142,7 @@ struct dso {
struct rb_root symbols[MAP__NR_TYPES];
struct rb_root symbol_names[MAP__NR_TYPES];
struct rb_root inlined_nodes;
+ struct rb_root srclines;
struct {
u64 addr;
struct symbol *symbol;
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 8b3c30d24b0b..e1c6d86f1936 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1681,11 +1681,22 @@ struct mem_info *sample__resolve_mem(struct perf_sample *sample,

static char *callchain_srcline(struct map *map, struct symbol *sym, u64 ip)
{
+ char *srcline = NULL;
+
if (!map || callchain_param.key == CCKEY_FUNCTION)
- return NULL;
+ return srcline;
+
+ srcline = srcline__tree_find(&map->dso->srclines, ip);
+ if (!srcline) {
+ bool show_sym = false;
+ bool show_addr = callchain_param.key == CCKEY_ADDRESS;
+
+ srcline = get_srcline(map->dso, map__rip_2objdump(map, ip),
+ sym, show_sym, show_addr);
+ srcline__tree_insert(&map->dso->srclines, ip, srcline);
+ }

- return get_srcline(map->dso, map__rip_2objdump(map, ip),
- sym, false, callchain_param.key == CCKEY_ADDRESS);
+ return srcline;
}

struct iterations {
diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
index a24bfcfa6174..bd96a6f231fc 100644
--- a/tools/perf/util/srcline.c
+++ b/tools/perf/util/srcline.c
@@ -540,6 +540,72 @@ char *get_srcline(struct dso *dso, u64 addr, struct symbol *sym,
return __get_srcline(dso, addr, sym, show_sym, show_addr, false);
}

+struct srcline_node {
+ u64 addr;
+ char *srcline;
+ struct rb_node rb_node;
+};
+
+void srcline__tree_insert(struct rb_root *tree, u64 addr, char *srcline)
+{
+ struct rb_node **p = &tree->rb_node;
+ struct rb_node *parent = NULL;
+ struct srcline_node *i, *node;
+
+ node = zalloc(sizeof(struct srcline_node));
+ if (!node) {
+ perror("not enough memory for the srcline node");
+ return;
+ }
+
+ node->addr = addr;
+ node->srcline = srcline;
+
+ while (*p != NULL) {
+ parent = *p;
+ i = rb_entry(parent, struct srcline_node, rb_node);
+ if (addr < i->addr)
+ p = &(*p)->rb_left;
+ else
+ p = &(*p)->rb_right;
+ }
+ rb_link_node(&node->rb_node, parent, p);
+ rb_insert_color(&node->rb_node, tree);
+}
+
+char *srcline__tree_find(struct rb_root *tree, u64 addr)
+{
+ struct rb_node *n = tree->rb_node;
+
+ while (n) {
+ struct srcline_node *i = rb_entry(n, struct srcline_node,
+ rb_node);
+
+ if (addr < i->addr)
+ n = n->rb_left;
+ else if (addr > i->addr)
+ n = n->rb_right;
+ else
+ return i->srcline;
+ }
+
+ return NULL;
+}
+
+void srcline__tree_delete(struct rb_root *tree)
+{
+ struct srcline_node *pos;
+ struct rb_node *next = rb_first(tree);
+
+ while (next) {
+ pos = rb_entry(next, struct srcline_node, rb_node);
+ next = rb_next(&pos->rb_node);
+ rb_erase(&pos->rb_node, tree);
+ free_srcline(pos->srcline);
+ zfree(&pos);
+ }
+}
+
struct inline_node *dso__parse_addr_inlines(struct dso *dso, u64 addr,
struct symbol *sym)
{
diff --git a/tools/perf/util/srcline.h b/tools/perf/util/srcline.h
index 0d2aca92e8c7..187a71082cb8 100644
--- a/tools/perf/util/srcline.h
+++ b/tools/perf/util/srcline.h
@@ -15,6 +15,13 @@ char *__get_srcline(struct dso *dso, u64 addr, struct symbol *sym,
bool show_sym, bool show_addr, bool unwind_inlines);
void free_srcline(char *srcline);

+// insert the srcline into the DSO, which will take ownership
+void srcline__tree_insert(struct rb_root *tree, u64 addr, char *srcline);
+// find previously inserted srcline
+char *srcline__tree_find(struct rb_root *tree, u64 addr);
+// delete all srclines within the tree
+void srcline__tree_delete(struct rb_root *tree);
+
#define SRCLINE_UNKNOWN ((char *) "??:0")

struct inline_list {
--
2.14.1