2019-11-27 17:52:42

by Jim Cromie

Subject: [PATCH 05/16] dyndbg: fix overcounting of ram used by dyndbg

during dyndbg init, verbose logging prints its ram overhead. It
counted strlens of struct _ddebug's 4 string members, in all callsite
entries, which would be approximately correct if each had been
mallocd. But they are pointers into shared .rodata; for example, all
10 kobject callsites have identical filename, module values.

Its best not to count that memory at all, since we cannot know they
were linked in because of CONFIG_DYNAMIC_DEBUG=y, and we want to
report a number that reflects what ram is saved by deconfiguring it.

Signed-off-by: Jim Cromie <[email protected]>
---
lib/dynamic_debug.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 0a4588fe342e..b5fb0aa0fbc3 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1008,7 +1008,6 @@ static int __init dynamic_debug_init(void)
char *cmdline;
int ret = 0;
int n = 0, entries = 0, modct = 0;
- int verbose_bytes = 0;

if (__start___dyndbg == __stop___dyndbg) {
pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
@@ -1019,9 +1018,6 @@ static int __init dynamic_debug_init(void)
iter_start = iter;
for (; iter < __stop___dyndbg; iter++) {
entries++;
- verbose_bytes += strlen(iter->modname) + strlen(iter->function)
- + strlen(iter->filename) + strlen(iter->format);
-
if (strcmp(modname, iter->modname)) {
modct++;
ret = ddebug_add_module(iter_start, n, modname);
@@ -1038,9 +1034,9 @@ static int __init dynamic_debug_init(void)
goto out_err;

ddebug_init_success = 1;
- vpr_info("%d modules, %d entries and %d bytes in ddebug tables, %d bytes in (readonly) verbose section\n",
+ vpr_info("%d modules, %d entries and %d bytes in ddebug tables, %d bytes in __dyndbg section\n",
modct, entries, (int)(modct * sizeof(struct ddebug_table)),
- verbose_bytes + (int)(__stop___dyndbg - __start___dyndbg));
+ (int)(entries * sizeof(struct _ddebug)));

/* apply ddebug_query boot param, dont unload tables on err */
if (ddebug_setup_string[0] != '\0') {
--
2.23.0

2019-11-28 08:23:14

by Rasmus Villemoes

Subject: Re: [PATCH 05/16] dyndbg: fix overcounting of ram used by dyndbg

On 27/11/2019 18.50, Jim Cromie wrote:
> during dyndbg init, verbose logging prints its ram overhead. It
> counted strlens of struct _ddebug's 4 string members, in all callsite
> entries, which would be approximately correct if each had been
> mallocd. But they are pointers into shared .rodata; for example, all
> 10 kobject callsites have identical filename, module values.
>
> Its best not to count that memory at all, since we cannot know they
> were linked in because of CONFIG_DYNAMIC_DEBUG=y, and we want to
> report a number that reflects what ram is saved by deconfiguring it.

That, and we avoid 1000s of (mostly cache-cold) strlen() calls during boot.

Acked-by: Rasmus Villemoes <[email protected]>

I'll see if I can find time to review the other patches, then I think
you need to resend with Andrew on the cc-list (added here). I think he's
the one routing lib/dynamic_debug.c patches.

Rasmus