Re: [PATCH] libgcov support for profile collection in region of interest (issue6186044)

[Jan Hubicka <hubicka at ucw dot cz>]

> +Honza and Nathan.
> 
> David
> 
> On Thu, May 3, 2012 at 10:52 AM, Teresa Johnson <tejohnson@google.com> wrote:
> > 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?

This seems resonable things to do.  You need to add an documentation and make sure they
go new L_* section, since not every app using libgcov needs necesarily those two.

Honza
> >
> > Thanks,
> > Teresa
> >
> > 2012-05-03 ? Teresa Johnson ?<tejohnson@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