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SubjectRe: [PATCH v2 -tip] perf probe: Add fastpath to do lookup by function name
(2011/03/24 23:09), Lin Ming wrote:
> 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.
>
> ./perf stat -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
> =====================
> 364.535892 task-clock-msecs # 0.997 CPUs
> 0 context-switches # 0.000 M/sec
> 0 CPU-migrations # 0.000 M/sec
> 29,993 page-faults # 0.082 M/sec
> 865,862,109 cycles # 2375.245 M/sec
> 1,255,259,630 instructions # 1.450 IPC
> 252,400,884 branches # 692.390 M/sec
> 3,429,376 branch-misses # 1.359 %
> 1,386,990 cache-references # 3.805 M/sec
> 687,188 cache-misses # 1.885 M/sec
>
> 0.365792170 seconds time elapsed
>
> after patch applied
> =====================
> 89.896405 task-clock-msecs # 0.991 CPUs
> 1 context-switches # 0.000 M/sec
> 0 CPU-migrations # 0.000 M/sec
> 10,145 page-faults # 0.113 M/sec
> 214,553,875 cycles # 2386.679 M/sec
> 226,915,559 instructions # 1.058 IPC
> 44,536,614 branches # 495.422 M/sec
> 613,074 branch-misses # 1.377 %
> 860,787 cache-references # 9.575 M/sec
> 442,380 cache-misses # 4.921 M/sec
>
> 0.090716032 seconds time elapsed

Thanks! Looks very good :)

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

>
> Signed-off-by: Lin Ming <ming.m.lin@intel.com>
> ---
> tools/perf/util/probe-finder.c | 39 +++++++++++++++++++++++++++++++++++++++
> tools/perf/util/probe-finder.h | 1 +
> 2 files changed, 40 insertions(+), 0 deletions(-)
>
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 194f9e2..5cf044c 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -1876,6 +1876,31 @@ static int find_line_range_by_func(struct line_finder *lf)
> return param.retval;
> }
>
> +static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
> +{
> + struct line_finder *lf = data;
> + struct line_range *lr = lf->lr;
> +
> + if (dwarf_offdie(dbg, gl->die_offset, &lf->sp_die)) {
> + if (dwarf_tag(&lf->sp_die) != DW_TAG_subprogram)
> + return DWARF_CB_OK;
> +
> + if (die_compare_name(&lf->sp_die, lr->function)) {
> + if (!dwarf_offdie(dbg, gl->cu_offset, &lf->cu_die))
> + return DWARF_CB_OK;
> +
> + if (lr->file &&
> + strtailcmp(lr->file, dwarf_decl_file(&lf->sp_die)))
> + return DWARF_CB_OK;
> +
> + lf->found = 1;
> + return DWARF_CB_ABORT;
> + }
> + }
> +
> + return DWARF_CB_OK;
> +}
> +
> int find_line_range(int fd, struct line_range *lr)
> {
> struct line_finder lf = {.lr = lr, .found = 0};
> @@ -1895,6 +1920,19 @@ 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 dwarf_callback_param param = {.data = (void *)&lf, .retval = 0};
> +
> + dwarf_getpubnames(dbg, pubname_search_cb, &lf, 0);
> + if (lf.found) {
> + lf.found = 0;
> + line_range_search_cb(&lf.sp_die, &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 +1961,7 @@ 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..4bc56a4 100644
> --- a/tools/perf/util/probe-finder.h
> +++ b/tools/perf/util/probe-finder.h
> @@ -83,6 +83,7 @@ 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@hitachi.com


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