This patch adds functionality to libgcov to enable user applications to
collect profile data only in regions of interest. This is useful, for
example, to collect profile data from a long-running server only
during the time when it is serving requests.
Specifically, the new routines __gcov_reset will clear all profile counters
to zero and __gcov_dump will write out the profile information collected so
far. A global variable is used to prevent writing out the profile a
second time during exit.
Bootstrapped and tested on x86_64-unknown-linux-gnu. Is this ok for trunk?
Thanks,
Teresa
2012-05-03 Teresa Johnson <tejohn...@google.com>
* libgcc/libgcov.c (gcov_clear, __gcov_reset): New functions.
(__gcov_dump): Ditto.
(gcov_dump_complete): New global variable.
(__gcov_flush): Outline functionality now in gcov_clear.
* gcc/gcov-io.h (__gcov_reset, __gcov_dump): Declare.
Index: libgcc/libgcov.c
===================================================================
--- libgcc/libgcov.c (revision 187048)
+++ libgcc/libgcov.c (working copy)
@@ -48,6 +48,8 @@ see the files COPYING3 and COPYING.RUNTIME respect
#ifdef L_gcov
void __gcov_init (struct gcov_info *p __attribute__ ((unused))) {}
void __gcov_flush (void) {}
+void __gcov_reset (void) {}
+void __gcov_dump (void) {}
#endif
#ifdef L_gcov_merge_add
@@ -91,6 +93,9 @@ static struct gcov_info *gcov_list;
/* Size of the longest file name. */
static size_t gcov_max_filename = 0;
+/* Flag when the profile has already been dumped via __gcov_dump(). */
+static int gcov_dump_complete = 0;
+
/* Make sure path component of the given FILENAME exists, create
missing directories. FILENAME must be writable.
Returns zero on success, or -1 if an error occurred. */
@@ -286,6 +291,11 @@ gcov_exit (void)
char *gi_filename, *gi_filename_up;
gcov_unsigned_t crc32 = 0;
+ /* Prevent the counters from being dumped a second time on exit when the
+ application already wrote out the profile using __gcov_dump(). */
+ if (gcov_dump_complete)
+ return;
+
memset (&all_prg, 0, sizeof (all_prg));
/* Find the totals for this execution. */
memset (&this_prg, 0, sizeof (this_prg));
@@ -679,6 +689,37 @@ gcov_exit (void)
}
}
+/* Reset all counters to zero. */
+
+static void
+gcov_clear (void)
+{
+ const struct gcov_info *gi_ptr;
+
+ for (gi_ptr = gcov_list; gi_ptr; gi_ptr = gi_ptr->next)
+ {
+ unsigned f_ix;
+
+ for (f_ix = 0; f_ix < gi_ptr->n_functions; f_ix++)
+ {
+ unsigned t_ix;
+ const struct gcov_fn_info *gfi_ptr = gi_ptr->functions[f_ix];
+
+ if (!gfi_ptr || gfi_ptr->key != gi_ptr)
+ continue;
+ const struct gcov_ctr_info *ci_ptr = gfi_ptr->ctrs;
+ for (t_ix = 0; t_ix != GCOV_COUNTERS; t_ix++)
+ {
+ if (!gi_ptr->merge[t_ix])
+ continue;
+
+ memset (ci_ptr->values, 0, sizeof (gcov_type) * ci_ptr->num);
+ ci_ptr++;
+ }
+ }
+ }
+}
+
/* Add a new object file onto the bb chain. Invoked automatically
when running an object file's global ctors. */
@@ -730,38 +771,38 @@ init_mx_once (void)
void
__gcov_flush (void)
{
- const struct gcov_info *gi_ptr;
-
init_mx_once ();
__gthread_mutex_lock (&__gcov_flush_mx);
gcov_exit ();
- for (gi_ptr = gcov_list; gi_ptr; gi_ptr = gi_ptr->next)
- {
- unsigned f_ix;
+ gcov_clear ();
- for (f_ix = 0; f_ix < gi_ptr->n_functions; f_ix++)
- {
- unsigned t_ix;
- const struct gcov_fn_info *gfi_ptr = gi_ptr->functions[f_ix];
+ __gthread_mutex_unlock (&__gcov_flush_mx);
+}
- if (!gfi_ptr || gfi_ptr->key != gi_ptr)
- continue;
- const struct gcov_ctr_info *ci_ptr = gfi_ptr->ctrs;
- for (t_ix = 0; t_ix != GCOV_COUNTERS; t_ix++)
- {
- if (!gi_ptr->merge[t_ix])
- continue;
-
- memset (ci_ptr->values, 0, sizeof (gcov_type) * ci_ptr->num);
- ci_ptr++;
- }
- }
- }
+/* Function that can be called from application to reset counters to zero,
+ in order to collect profile in region of interest. */
- __gthread_mutex_unlock (&__gcov_flush_mx);
+void
+__gcov_reset (void)
+{
+ gcov_clear ();
+ /* Re-enable dumping to support collecting profile in multiple regions
+ of interest. */
+ gcov_dump_complete = 0;
}
+/* Function that can be called from application to write profile collected
+ so far, in order to collect profile in region of interest. */
+
+void
+__gcov_dump (void)
+{
+ gcov_exit ();
+ /* Prevent profile from being dumped a second time on application exit. */
+ gcov_dump_complete = 1;
+}
+
#endif /* L_gcov */
#ifdef L_gcov_merge_add
Index: gcc/gcov-io.h
===================================================================
--- gcc/gcov-io.h (revision 187048)
+++ gcc/gcov-io.h (working copy)
@@ -458,6 +458,12 @@ extern void __gcov_init (struct gcov_info *) ATTRI
/* Called before fork, to avoid double counting. */
extern void __gcov_flush (void) ATTRIBUTE_HIDDEN;
+/* Function to reset all counters to 0. */
+extern void __gcov_reset (void);
+
+/* Function to enable early write of profile information so far. */
+extern void __gcov_dump (void);
+
/* The merge function that just sums the counters. */
extern void __gcov_merge_add (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
--
This patch is available for review at http://codereview.appspot.com/6186044
