perf symbol: Remove symbol_name_rb_node

Most perf commands want to sort symbols by name and this is done via
an invasive rbtree that on 64-bit systems costs 24 bytes. Sorting the
symbols in a DSO by name is optional and not done by default, however,
if sorting is requested the 24 bytes is allocated for every
symbol.

This change removes the rbtree and uses a sorted array of symbol
pointers instead (costing 8 bytes per symbol). As the array is created
on demand then there are further memory savings. The complexity of
sorting the array and using the rbtree are the same.

To support going to the next symbol, the index of the current symbol
needs to be passed around as a pair with the current symbol. This
requires some API changes.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Carsten Haitzler <carsten.haitzler@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Jason Wang <wangborong@cdjrlc.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/20230623054520.4118442-3-irogers@google.com
[ minimize change in symbols__sort_by_name() ]
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index b23a157c914d..b41c9782c754 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -150,7 +150,8 @@ struct dso {
 	struct rb_node	 rb_node;	/* rbtree node sorted by long name */
 	struct rb_root	 *root;		/* root of rbtree that rb_node is in */
 	struct rb_root_cached symbols;
-	struct rb_root_cached symbol_names;
+	struct symbol	 **symbol_names;
+	size_t		 symbol_names_len;
 	struct rb_root_cached inlined_nodes;
 	struct rb_root_cached srclines;
 	struct {