dyndbg: fix overcounting of ram used by dyndbg (81d0c2c6) · Commits · 戴 / test

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. Also fix wording and size under-reporting of the __dyndbg section. Heres my overhead, on a virtme-run VM on a fedora-31 laptop: dynamic_debug:dynamic_debug_init: 260 modules, 2479 entries \ and 10400 bytes in ddebug tables, 138824 bytes in __dyndbg section Acked-by:

<jbaron@akamai.com> Signed-off-by:

Jim Cromie <jim.cromie@gmail.com> Link: https://lore.kernel.org/r/20200719231058.1586423-7-jim.cromie@gmail.com Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

lib/dynamic_debug.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -1017,7 +1017,6 @@ 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) {
		if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) {
		@@ -1033,9 +1032,6 @@ 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);
		@@ -1052,9 +1048,9 @@ 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') {

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