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Commit cd25f8bc authored by Lin Ming's avatar Lin Ming Committed by Arnaldo Carvalho de Melo
Browse files

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: default avatarMasami 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: default avatarLin Ming <ming.m.lin@intel.com>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent ca6a4258

tools/perf/util/probe-finder.c

+72 −0
Original line number Original line Diff line number Diff line
@@ -1435,6 +1435,38 @@ static int find_probe_point_by_func(struct probe_finder *pf) 
	return _param.retval;

	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 */

/* Find probe points from debuginfo */

static int find_probes(int fd, struct probe_finder *pf)

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;

	off = 0;

	line_list__init(&pf->lcache);

	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) */

	/* Loop on CUs (Compilation Unit) */

	while (!dwarf_nextcu(dbg, off, &noff, &cuhl, NULL, NULL, NULL)) {

	while (!dwarf_nextcu(dbg, off, &noff, &cuhl, NULL, NULL, NULL)) {

		/* Get the DIE(Debugging Information Entry) of this CU */

		/* 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;

		off = noff;

	}

	}



found:

	line_list__free(&pf->lcache);

	line_list__free(&pf->lcache);

	if (dwfl)

	if (dwfl)

		dwfl_end(dwfl);

		dwfl_end(dwfl);
@@ -1895,6 +1950,22 @@ int find_line_range(int fd, struct line_range *lr) 
		return -EBADF;

		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) */

	/* Loop on CUs (Compilation Unit) */

	while (!lf.found && ret >= 0) {

	while (!lf.found && ret >= 0) {

		if (dwarf_nextcu(dbg, off, &noff, &cuhl, NULL, NULL, NULL) != 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;

		off = noff;

	}

	}





found:

	/* Store comp_dir */

	/* Store comp_dir */

	if (lf.found) {

	if (lf.found) {

		comp_dir = cu_get_comp_dir(&lf.cu_die);

		comp_dir = cu_get_comp_dir(&lf.cu_die);

tools/perf/util/probe-finder.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -49,6 +49,7 @@ struct probe_finder { 
	Dwarf_Addr		addr;		/* Address */

	Dwarf_Addr		addr;		/* Address */

	const char		*fname;		/* Real file name */

	const char		*fname;		/* Real file name */

	Dwarf_Die		cu_die;		/* Current CU */

	Dwarf_Die		cu_die;		/* Current CU */

	Dwarf_Die		sp_die;

	struct list_head	lcache;		/* Line cache for lazy match */

	struct list_head	lcache;		/* Line cache for lazy match */





	/* For variable searching */

	/* For variable searching */
@@ -83,6 +84,7 @@ struct line_finder { 
	int			lno_s;		/* Start line number */

	int			lno_s;		/* Start line number */

	int			lno_e;		/* End line number */

	int			lno_e;		/* End line number */

	Dwarf_Die		cu_die;		/* Current CU */

	Dwarf_Die		cu_die;		/* Current CU */

	Dwarf_Die		sp_die;

	int			found;

	int			found;

};

};