ftrace: Speed up search by skipping pages by address

As all records in a page of the ftrace table are sorted, we can
speed up the search algorithm by checking if the address to look for
falls in between the first and last record ip on the page.

This speeds up both the ftrace_location() and ftrace_text_reserved()
algorithms, as it can skip full pages when the search address is
not in them.

Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index e10f9e522c44b0a96ab7dbae297e3ae2b4aeb3ed..fc93562a66541ec114c400813b3e6fb9f166d664 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1411,6 +1411,8 @@ int ftrace_location(unsigned long ip)
        key.ip = ip;
 
        for (pg = ftrace_pages_start; pg; pg = pg->next) {
+               if (ip < pg->records[0].ip || ip > pg->records[pg->index - 1].ip)
+                       continue;
                rec = bsearch(&key, pg->records, pg->index,
                              sizeof(struct dyn_ftrace),
                              ftrace_cmp_recs);
@@ -1571,16 +1573,24 @@ void ftrace_bug(int failed, unsigned long ip)
 
 
 /* Return 1 if the address range is reserved for ftrace */
-int ftrace_text_reserved(void *start, void *end)
+int ftrace_text_reserved(void *s, void *e)
 {
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;
+       unsigned long start = (unsigned long)s;
+       unsigned long end = (unsigned long)e;
+       int i;
 
-       do_for_each_ftrace_rec(pg, rec) {
-               if (rec->ip <= (unsigned long)end &&
-                   rec->ip + MCOUNT_INSN_SIZE > (unsigned long)start)
-                       return 1;
-       } while_for_each_ftrace_rec();
+       for (pg = ftrace_pages_start; pg; pg = pg->next) {
+               if (end < pg->records[0].ip ||
+                   start >= (pg->records[pg->index - 1].ip + MCOUNT_INSN_SIZE))
+                       continue;
+               for (i = 0; i < pg->index; i++) {
+                       rec = &pg->records[i];
+                       if (rec->ip <= end && rec->ip + MCOUNT_INSN_SIZE > start)
+                               return 1;
+               }
+       }
        return 0;
 }