[PATCH v2 04/18] perf map_browser: Compute symbol browser index on demand

[Ian Rogers <irogers@google.com>]

To wrap struct symbol in DECLARE_RC_STRUCT(symbol) and reduce per-symbol
memory overhead, negative-offset allocations ahead of struct symbol via
symbol_conf.priv_size and symbol__priv() need to be eliminated.

Remove symbol__browser_index() in ui/browsers/map.c and compute the TUI
map browser index on demand in map_browser__search() by walking the map
browser's symbol entries when the user searches with '/'.

While this changes finding a symbol's display row index in
map_browser__search() from O(1) to O(N) in the number of symbols in that
single map, map_browser__search() is only invoked interactively when a
user opens the TUI "Browse map details" view for a map, presses '/',
types a query, and hits ENTER. Even for a large DSO such as vmlinux
(~100k symbols), scanning the map's symbols once per interactive search
takes well under a millisecond (and becomes a flat pointer array scan
once symbols are stored in struct symbols).

Previously, '/' search in the TUI map browser was gated behind
'verbose > 0' (-v) in builtin-c2c.c, builtin-report.c, and
ui/browsers/map.c solely to avoid adding sizeof(u32) to
symbol_conf.priv_size for every struct symbol across all DSOs in normal
runs. With on-demand index computation there is no per-symbol memory
overhead, so remove the verbose > 0 restriction and allow '/' search in
the map browser unconditionally.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/builtin-c2c.c     | 14 --------------
 tools/perf/builtin-report.c  | 14 --------------
 tools/perf/ui/browsers/map.c | 37 ++++++++++++++++++------------------
 3 files changed, 18 insertions(+), 47 deletions(-)

diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
index f51fa23f3bf1..719f47dac2dc 100644
--- a/tools/perf/builtin-c2c.c
+++ b/tools/perf/builtin-c2c.c
@@ -3412,20 +3412,6 @@ static int perf_c2c__report(int argc, const char **argv)
 
 		if (ret < 0)
 			goto out_mem2node;
-		/*
-		 * For searching by name on the "Browse map details".
-		 * providing it only in verbose mode not to bloat too
-		 * much struct symbol.
-		 */
-		if (verbose > 0) {
-			/*
-			 * XXX: Need to provide a less kludgy way to ask for
-			 * more space per symbol, the u32 is for the index on
-			 * the ui browser.
-			 * See symbol__browser_index.
-			 */
-			symbol_conf.priv_size += sizeof(u32);
-		}
 		annotation_config__init();
 	}
 
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 29085fdc91e5..6672a4d16529 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -1885,20 +1885,6 @@ int cmd_report(int argc, const char **argv)
 		ret = symbol__annotation_init();
 		if (ret < 0)
 			goto error;
-		/*
- 		 * For searching by name on the "Browse map details".
- 		 * providing it only in verbose mode not to bloat too
- 		 * much struct symbol.
- 		 */
-		if (verbose > 0) {
-			/*
-			 * XXX: Need to provide a less kludgy way to ask for
-			 * more space per symbol, the u32 is for the index on
-			 * the ui browser.
-			 * See symbol__browser_index.
-			 */
-			symbol_conf.priv_size += sizeof(u32);
-		}
 		annotation_config__init();
 	}
 
diff --git a/tools/perf/ui/browsers/map.c b/tools/perf/ui/browsers/map.c
index 47f2743cae26..2f070a53b5cb 100644
--- a/tools/perf/ui/browsers/map.c
+++ b/tools/perf/ui/browsers/map.c
@@ -39,12 +39,6 @@ static void map_browser__write(struct ui_browser *browser, void *nd, int row)
 		ui_browser__write_nstring(browser, symbol__name(sym), width);
 }
 
-/* FIXME uber-kludgy, see comment on cmd_report... */
-static u32 *symbol__browser_index(struct symbol *browser)
-{
-	return ((void *)browser) - sizeof(struct rb_node) - sizeof(u32);
-}
-
 static int map_browser__search(struct map_browser *browser)
 {
 	char target[512];
@@ -62,10 +56,21 @@ static int map_browser__search(struct map_browser *browser)
 		sym = map__find_symbol_by_name(browser->map, target);
 
 	if (sym != NULL) {
-		u32 *idx = symbol__browser_index(sym);
-
-		browser->b.top = &sym->rb_node;
-		browser->b.index = browser->b.top_idx = *idx;
+		struct rb_node *nd;
+		u32 idx = 0;
+
+		/*
+		 * Walk the map browser's symbol entries to find the matching
+		 * symbol node and its display row index, then position the
+		 * browser cursor at that entry.
+		 */
+		for (nd = rb_first(browser->b.entries); nd; nd = rb_next(nd), ++idx) {
+			if (&sym->rb_node == nd) {
+				browser->b.top = nd;
+				browser->b.index = browser->b.top_idx = idx;
+				break;
+			}
+		}
 	} else
 		ui_helpline__fpush("%s not found!", target);
 
@@ -77,8 +82,7 @@ static int map_browser__run(struct map_browser *browser)
 	int key;
 
 	if (ui_browser__show(&browser->b, dso__long_name(map__dso(browser->map)),
-			     "Press ESC to exit, %s / to search",
-			     verbose > 0 ? "" : "restart with -v to use") < 0)
+			     "Press ESC to exit, / to search") < 0)
 		return -1;
 
 	while (1) {
@@ -86,9 +90,8 @@ static int map_browser__run(struct map_browser *browser)
 
 		switch (key) {
 		case '/':
-			if (verbose > 0)
-				map_browser__search(browser);
-			/* fall thru */
+			map_browser__search(browser);
+			continue;
 		default:
 			ui_browser__warn_unhandled_hotkey(&browser->b, key, 0, NULL);
 			continue;
@@ -124,10 +127,6 @@ int map__browse(struct map *map)
 
 		if (maxaddr < symbol__end(pos))
 			maxaddr = symbol__end(pos);
-		if (verbose > 0) {
-			u32 *idx = symbol__browser_index(pos);
-			*idx = mb.b.nr_entries;
-		}
 		++mb.b.nr_entries;
 	}
 
-- 
2.56.0.313.g2479322e68-goog