Re: [PATCH v1 2/2] perf dsos: When adding a dso into sorted dsos maintain the sort order

From: Namhyung Kim
Date: Wed Jul 03 2024 - 17:46:46 EST


On Wed, Jul 03, 2024 at 10:21:17AM -0700, Ian Rogers wrote:
> dsos__add would add at the end of the dso array possibly requiring a
> later find to re-sort the array. Patterns of find then add were
> becoming O(n*log n) due to the sorts. Change the add routine to be
> O(n) rather than O(1) but to maintain the sorted-ness of the dsos
> array so that later finds don't need the O(n*log n) sort.
>
> Reported-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>

It works well for me too!

Tested-by: Namhyung Kim <namhyung@xxxxxxxxxx>

Thanks,
Namhyung

> ---
> tools/perf/util/dsos.c | 26 +++++++++++++++++++++-----
> 1 file changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c
> index 5e5e05f86dd3..d4acdb37f046 100644
> --- a/tools/perf/util/dsos.c
> +++ b/tools/perf/util/dsos.c
> @@ -206,11 +206,27 @@ int __dsos__add(struct dsos *dsos, struct dso *dso)
> dsos->dsos = temp;
> dsos->allocated = to_allocate;
> }
> - dsos->dsos[dsos->cnt++] = dso__get(dso);
> - if (dsos->cnt >= 2 && dsos->sorted) {
> - dsos->sorted = dsos__cmp_long_name_id_short_name(&dsos->dsos[dsos->cnt - 2],
> - &dsos->dsos[dsos->cnt - 1])
> - <= 0;
> + if (!dsos->sorted) {
> + dsos->dsos[dsos->cnt++] = dso__get(dso);
> + } else {
> + int low = 0, high = dsos->cnt - 1;
> + int insert = dsos->cnt; /* Default to inserting at the end. */
> +
> + while (low <= high) {
> + int mid = low + (high - low) / 2;
> + int cmp = dsos__cmp_long_name_id_short_name(&dsos->dsos[mid], &dso);
> +
> + if (cmp < 0) {
> + low = mid + 1;
> + } else {
> + high = mid - 1;
> + insert = mid;
> + }
> + }
> + memmove(&dsos->dsos[insert + 1], &dsos->dsos[insert],
> + (dsos->cnt - insert) * sizeof(struct dso *));
> + dsos->cnt++;
> + dsos->dsos[insert] = dso__get(dso);
> }
> dso__set_dsos(dso, dsos);
> return 0;
> --
> 2.45.2.803.g4e1b14247a-goog
>