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>

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 194f9e2..ff416b8 100644 (file)
--- 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 beaefc3..605730a 100644 (file)
--- 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;
 };