Commit 15218296 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'ftrace-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace 

Pull ftrace update from Steven Rostedt:

 - Speed up ftrace_lookup_symbols() for single lookups

   The kallsyms lookup in ftrace_lookup_symbols() does a linear search
   over each symbol. This is fine when it must match multiple strings,
   but when there's only a single string being searched for, using a
   binary search is much more efficient. When a single string is passed
   in to search, use the binary search method.

* tag 'ftrace-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ftrace: Use kallsyms binary search for single-symbol lookup
parents aec2f682 93e8fd1a

kernel/trace/ftrace.c

+22 −0
Original line number Diff line number Diff line
@@ -9267,6 +9267,15 @@ static int kallsyms_callback(void *data, const char *name, unsigned long addr) 
 * @addrs array, which needs to be big enough to store at least @cnt

 * addresses.

 *

 * For a single symbol (cnt == 1), uses kallsyms_lookup_name() which

 * performs an O(log N) binary search via the sorted kallsyms index.

 * This avoids the full O(N) linear scan over all kernel symbols that

 * the multi-symbol path requires.

 *

 * For multiple symbols, uses a single-pass linear scan via

 * kallsyms_on_each_symbol() with binary search into the sorted input

 * array.

 *

 * Returns: 0 if all provided symbols are found, -ESRCH otherwise.

 */

int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs)
@@ -9274,6 +9283,19 @@ int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *a 
	struct kallsyms_data args;

	int found_all;



	/* Fast path: single symbol uses O(log N) binary search */

	if (cnt == 1) {

		addrs[0] = kallsyms_lookup_name(sorted_syms[0]);

		if (addrs[0] && ftrace_location(addrs[0]))

			return 0;

		/*

		 * Binary lookup can fail for duplicate symbol names

		 * where the first match is not ftrace-instrumented.

		 * Retry with linear scan.

		 */

	}



	/* Batch path: single-pass O(N) linear scan */

	memset(addrs, 0, sizeof(*addrs) * cnt);

	args.addrs = addrs;

	args.syms = sorted_syms;