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>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 2d6f8bcd18842311b8ef40851070e074f536eaf6..dcd3a814d39b0a258578f15ad9807b38427647a2 100644 (file)
--- 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)