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From:   Jim Cromie <jim.cromie@gmail.com>
To:     jbaron@akamai.com, linux-kernel@vger.kernel.org
Cc:     Jim Cromie <jim.cromie@gmail.com>
Subject: [PATCH 2/7] dyndbg: motivate a diet plan
Date:   Fri,  7 Aug 2020 14:09:49 -0600
Message-Id: <20200807200957.1269454-3-jim.cromie@gmail.com>
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this throwaway patch demonstrates the extra weight:

 dyndbg: 2605 entries. repeated entries: 2369 module 2231 file 1147 func

Thats (91%, 86%, 44%) repeated values in those pointers/columns.

This simple test also shows that a similarly simple run-length encoder
on those 3 columns would compress this table dramatically.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 lib/dynamic_debug.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 01b7d0210412..691e79826fc2 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1059,11 +1059,12 @@ static int __init dynamic_debug_init_control(void)
 
 static int __init dynamic_debug_init(void)
 {
-	struct _ddebug *iter, *iter_start;
+	struct _ddebug *iter, *iter_start, *prev = 0;
 	const char *modname = NULL;
 	char *cmdline;
 	int ret = 0;
 	int n = 0, entries = 0, modct = 0;
+	int modreps = 0, funcreps = 0, filereps = 0;
 
 	if (&__start___dyndbg == &__stop___dyndbg) {
 		if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) {
@@ -1077,7 +1078,16 @@ static int __init dynamic_debug_init(void)
 	iter = __start___dyndbg;
 	modname = iter->modname;
 	iter_start = iter;
-	for (; iter < __stop___dyndbg; iter++) {
+	for (prev = iter; iter < __stop___dyndbg; iter++) {
+		if (entries) {
+			if (prev->site->modname == iter->site->modname)
+				modreps++;
+			if (prev->site->function == iter->site->function)
+				funcreps++;
+			if (prev->site->filename == iter->site->filename)
+				filereps++;
+			prev++; /* one behind iter */
+		}
 		entries++;
 		if (strcmp(modname, iter->modname)) {
 			modct++;
@@ -1099,6 +1109,9 @@ static int __init dynamic_debug_init(void)
 		 modct, entries, (int)(modct * sizeof(struct ddebug_table)),
 		 (int)(entries * sizeof(struct _ddebug)));
 
+	vpr_info("%d entries. repeated entries: %d module %d file %d func\n",
+		 entries, modreps, filereps, funcreps);
+
 	/* apply ddebug_query boot param, dont unload tables on err */
 	if (ddebug_setup_string[0] != '\0') {
 		pr_warn("ddebug_query param name is deprecated, change it to dyndbg\n");
-- 
2.26.2