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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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