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Date: Mon, 28 Mar 2011 10:02:38 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Lin Ming <ming.m.lin@...el.com>
Cc: Arnaldo Carvalho de Melo <acme@...radead.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...e.hu>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip v3] perf probe: Add fastpath to do lookup by function
name
(2011/03/25 17:27), Lin Ming wrote:
> v3 -> v2:
> - Make pubname_search_cb more generic
> - Add fastpath to find_probes also
Good catch! :)
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Thank you,
>
> 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
>
> Signed-off-by: Lin Ming <ming.m.lin@...el.com>
> ---
> tools/perf/util/probe-finder.c | 68 ++++++++++++++++++++++++++++++++++++++++
> tools/perf/util/probe-finder.h | 2 +
> 2 files changed, 70 insertions(+), 0 deletions(-)
>
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 194f9e2..23fc9eb 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 +1493,23 @@ 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, .found = 0};
> + struct dwarf_callback_param probe_param = {
> + .data = (void *)pf, .retval = 0};
> +
> + 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 +1537,8 @@ 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 +1946,22 @@ 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 +1990,7 @@ 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
> --- 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;
> };
>
--
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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