perf probe: Add fastpath to do lookup by function name

v3 -> v2:
- Make pubname_search_cb more generic
- Add fastpath to find_probes also

v2 -> v1:
- Don't compare file names with cu_find_realpath(...), instead, compare
  them with the name returned by dwarf_decl_file(sp_die)

The vmlinux file may have thousands of CUs.
We can lookup function name from .debug_pubnames section
to avoid the slow loop on CUs.

1. Improvement data for find_line_range

./perf stat -e cycles -r 10 -- ./perf probe -k /home/mlin/vmlinux \
        -s /home/mlin/linux-2.6 \
        --line csum_partial_copy_to_user > tmp.log

before patch applied
=====================
       847,988,276 cycles

        0.355075856  seconds time elapsed

after patch applied
=====================
       206,102,622 cycles

        0.086883555  seconds time elapsed

2. Improvement data for find_probes

./perf stat -e cycles -r 10 -- ./perf probe -k /home/mlin/vmlinux \
        -s /home/mlin/linux-2.6 \
        --vars csum_partial_copy_to_user > tmp.log

before patch applied
=====================
       848,490,844 cycles

        0.355307901  seconds time elapsed

after patch applied
=====================
       205,684,469 cycles

        0.086694010  seconds time elapsed

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
LKML-Reference: <1301041668.14111.52.camel@minggr.sh.intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 74 insertions, 0 deletions

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 194f9e2a3285..ff416b85f7e8 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1435,6 +1435,38 @@ static int find_probe_point_by_func(struct probe_finder *pf)
         return _param.retval;
 }
 
+struct pubname_callback_param {
+        char *function;
+        char *file;
+        Dwarf_Die *cu_die;
+        Dwarf_Die *sp_die;
+        int found;
+};
+
+static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
+{
+        struct pubname_callback_param *param = data;
+
+        if (dwarf_offdie(dbg, gl->die_offset, param->sp_die)) {
+                if (dwarf_tag(param->sp_die) != DW_TAG_subprogram)
+                        return DWARF_CB_OK;
+
+                if (die_compare_name(param->sp_die, param->function)) {
+                        if (!dwarf_offdie(dbg, gl->cu_offset, param->cu_die))
+                                return DWARF_CB_OK;
+
+                        if (param->file &&
+                            strtailcmp(param->file, dwarf_decl_file(param->sp_die)))
+                                return DWARF_CB_OK;
+
+                        param->found = 1;
+                        return DWARF_CB_ABORT;
+                }
+        }
+
+        return DWARF_CB_OK;
+}
+
 /* Find probe points from debuginfo */
 static int find_probes(int fd, struct probe_finder *pf)
 {
@@ -1461,6 +1493,27 @@ static int find_probes(int fd, struct probe_finder *pf)
 
         off = 0;
         line_list__init(&pf->lcache);
+
+        /* Fastpath: lookup by function name from .debug_pubnames section */
+        if (pp->function) {
+                struct pubname_callback_param pubname_param = {
+                        .function = pp->function,
+                        .file     = pp->file,
+                        .cu_die   = &pf->cu_die,
+                        .sp_die   = &pf->sp_die,
+                };
+                struct dwarf_callback_param probe_param = {
+                        .data = pf,
+                };
+
+                dwarf_getpubnames(dbg, pubname_search_cb, &pubname_param, 0);
+                if (pubname_param.found) {
+                        ret = probe_point_search_cb(&pf->sp_die, &probe_param);
+                        if (ret)
+                                goto found;
+                }
+        }
+
         /* Loop on CUs (Compilation Unit) */
         while (!dwarf_nextcu(dbg, off, &noff, &cuhl, NULL, NULL, NULL)) {
                 /* Get the DIE(Debugging Information Entry) of this CU */
@@ -1488,6 +1541,8 @@ static int find_probes(int fd, struct probe_finder *pf)
                 }
                 off = noff;
         }
+
+found:
         line_list__free(&pf->lcache);
         if (dwfl)
                 dwfl_end(dwfl);
@@ -1895,6 +1950,22 @@ int find_line_range(int fd, struct line_range *lr)
                 return -EBADF;
         }
 
+        /* Fastpath: lookup by function name from .debug_pubnames section */
+        if (lr->function) {
+                struct pubname_callback_param pubname_param = {
+                        .function = lr->function, .file = lr->file,
+                        .cu_die = &lf.cu_die, .sp_die = &lf.sp_die, .found = 0};
+                struct dwarf_callback_param line_range_param = {
+                        .data = (void *)&lf, .retval = 0};
+
+                dwarf_getpubnames(dbg, pubname_search_cb, &pubname_param, 0);
+                if (pubname_param.found) {
+                        line_range_search_cb(&lf.sp_die, &line_range_param);
+                        if (lf.found)
+                                goto found;
+                }
+        }
+
         /* Loop on CUs (Compilation Unit) */
         while (!lf.found && ret >= 0) {
                 if (dwarf_nextcu(dbg, off, &noff, &cuhl, NULL, NULL, NULL) != 0)
@@ -1923,6 +1994,7 @@ int find_line_range(int fd, struct line_range *lr)
                 off = noff;
         }
 
+found:
         /* Store comp_dir */
         if (lf.found) {
                 comp_dir = cu_get_comp_dir(&lf.cu_die);
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index beaefc3c1223..605730a366db 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -49,6 +49,7 @@ struct probe_finder {
         Dwarf_Addr              addr;           /* Address */
         const char              *fname;         /* Real file name */
         Dwarf_Die               cu_die;         /* Current CU */
+        Dwarf_Die               sp_die;
         struct list_head        lcache;         /* Line cache for lazy match */
 
         /* For variable searching */
@@ -83,6 +84,7 @@ struct line_finder {
         int                     lno_s;          /* Start line number */
         int                     lno_e;          /* End line number */
         Dwarf_Die               cu_die;         /* Current CU */
+        Dwarf_Die               sp_die;
         int                     found;
 };