ftrace: Use bsearch to find record ip

Now that each set of pages in the function list are sorted by
ip, we can use bsearch to find a record within each set of pages.
This speeds up the ftrace_location() function by magnitudes.

For archs (like x86) that need to add a breakpoint at every function
that will be converted from a nop to a callback and vice versa,
the breakpoint callback needs to know if the breakpoint was for
ftrace or not. It requires finding the breakpoint ip within the
records. Doing a linear search is extremely inefficient. It is
a must to be able to do a fast binary search to find these locations.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 23 insertions, 15 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 2d6f8bcd188..dcd3a814d39 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -22,6 +22,7 @@
 #include <linux/hardirq.h>
 #include <linux/kthread.h>
 #include <linux/uaccess.h>
+#include <linux/bsearch.h>
 #include <linux/module.h>
 #include <linux/ftrace.h>
 #include <linux/sysctl.h>
@@ -1300,6 +1301,19 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip)
                 }                               \
         }
 
+
+static int ftrace_cmp_recs(const void *a, const void *b)
+{
+        const struct dyn_ftrace *reca = a;
+        const struct dyn_ftrace *recb = b;
+
+        if (reca->ip > recb->ip)
+                return 1;
+        if (reca->ip < recb->ip)
+                return -1;
+        return 0;
+}
+
 /**
  * ftrace_location - return true if the ip giving is a traced location
  * @ip: the instruction pointer to check
@@ -1313,11 +1327,17 @@ int ftrace_location(unsigned long ip)
 {
         struct ftrace_page *pg;
         struct dyn_ftrace *rec;
+        struct dyn_ftrace key;
 
-        do_for_each_ftrace_rec(pg, rec) {
-                if (rec->ip == ip)
+        key.ip = ip;
+
+        for (pg = ftrace_pages_start; pg; pg = pg->next) {
+                rec = bsearch(&key, pg->records, pg->index,
+                              sizeof(struct dyn_ftrace),
+                              ftrace_cmp_recs);
+                if (rec)
                         return 1;
-        } while_for_each_ftrace_rec();
+        }
 
         return 0;
 }
@@ -3587,18 +3607,6 @@ static void ftrace_swap_recs(void *a, void *b, int size)
         *recb = t;
 }
 
-static int ftrace_cmp_recs(const void *a, const void *b)
-{
-        const struct dyn_ftrace *reca = a;
-        const struct dyn_ftrace *recb = b;
-
-        if (reca->ip > recb->ip)
-                return 1;
-        if (reca->ip < recb->ip)
-                return -1;
-        return 0;
-}
-
 static int ftrace_process_locs(struct module *mod,
                                unsigned long *start,
                                unsigned long *end)