Hi,
this is my attempt to bring GCC into wonderful era of multicore CPUs :)
It is a hack, but it seems to help quite a lot. About 50% of WPA time is spent
by streaming the individual ltrans .o files. This can be easily parallelized
by fork - we do nothing afterwards, just exit and pass the list to the linker.
So until we are thread safe, perhaps this may be a solution? (or on unixish
systems probably it can be solution forever) I added a logic parsing -flto=24
and do number of streaming processes user asked for.
For -flto=jobserver I simply fork all 32 processes. It may not be a disaster,
but perhaps we should figure out how to communicate with jobserver. At first
glance on document on how it works, it seems easy to add. Perhaps we can even
convicne GNU Make folks to put simple helpers to libiberty?
We also may figure out number of CPUs (is it available i.e. from libgomp)
and use it by default even if user do not care to pass number of processes.
Naturally these streaming forks should be cheap memory wise. I hope Martin
will get me some actual numbers.
With the patch the WPA time of firefox goes down to 2 minutes (4.8 needs about
30 minutes and without the hack one needs about 5 minutes)
Before:
Execution times (seconds)
phase setup : 0.01 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 0%) wall
1398 kB ( 0%) ggc
phase opt and generate : 39.73 (17%) usr 0.49 ( 3%) sys 40.26 (16%) wall
347726 kB ( 5%) ggc
phase stream in : 82.43 (35%) usr 2.15 (14%) sys 84.62 (34%) wall
5970152 kB (94%) ggc
phase stream out : 114.05 (48%) usr 12.86 (83%) sys 127.26 (50%) wall
6868 kB ( 0%) ggc
garbage collection : 3.07 ( 1%) usr 0.00 ( 0%) sys 3.08 ( 1%) wall
0 kB ( 0%) ggc
callgraph optimization : 0.34 ( 0%) usr 0.00 ( 0%) sys 0.33 ( 0%) wall
30 kB ( 0%) ggc
ipa dead code removal : 4.91 ( 2%) usr 0.11 ( 1%) sys 5.16 ( 2%) wall
113 kB ( 0%) ggc
ipa inheritance graph : 0.12 ( 0%) usr 0.00 ( 0%) sys 0.12 ( 0%) wall
927 kB ( 0%) ggc
ipa virtual call target : 5.11 ( 2%) usr 0.05 ( 0%) sys 4.99 ( 2%) wall
55296 kB ( 1%) ggc
ipa cp : 2.65 ( 1%) usr 0.17 ( 1%) sys 2.80 ( 1%) wall
188629 kB ( 3%) ggc
ipa inlining heuristics : 18.49 ( 8%) usr 0.29 ( 2%) sys 18.79 ( 7%) wall
439981 kB ( 7%) ggc
ipa lto gimple in : 0.12 ( 0%) usr 0.01 ( 0%) sys 0.15 ( 0%) wall
0 kB ( 0%) ggc
ipa lto gimple out : 16.66 ( 7%) usr 1.26 ( 8%) sys 17.97 ( 7%) wall
0 kB ( 0%) ggc
ipa lto decl in : 68.70 (29%) usr 1.50 (10%) sys 70.23 (28%) wall
5181795 kB (82%) ggc
ipa lto decl out : 93.09 (39%) usr 4.93 (32%) sys 98.07 (39%) wall
0 kB ( 0%) ggc
ipa lto cgraph I/O : 1.65 ( 1%) usr 0.27 ( 2%) sys 1.92 ( 1%) wall
428974 kB ( 7%) ggc
ipa lto decl merge : 3.66 ( 2%) usr 0.00 ( 0%) sys 3.65 ( 1%) wall
8288 kB ( 0%) ggc
ipa lto cgraph merge : 3.42 ( 1%) usr 0.00 ( 0%) sys 3.42 ( 1%) wall
13725 kB ( 0%) ggc
whopr wpa : 3.58 ( 2%) usr 0.02 ( 0%) sys 3.59 ( 1%) wall
6871 kB ( 0%) ggc
whopr wpa I/O : 0.99 ( 0%) usr 6.65 (43%) sys 7.92 ( 3%) wall
0 kB ( 0%) ggc
whopr partitioning : 2.63 ( 1%) usr 0.01 ( 0%) sys 2.66 ( 1%) wall
0 kB ( 0%) ggc
ipa reference : 3.08 ( 1%) usr 0.08 ( 1%) sys 3.18 ( 1%) wall
0 kB ( 0%) ggc
whopr partitioning : 2.63 ( 1%) usr 0.01 ( 0%) sys 2.66 ( 1%) wall
0 kB ( 0%) ggc
ipa reference : 3.08 ( 1%) usr 0.08 ( 1%) sys 3.18 ( 1%) wall
0 kB ( 0%) ggc
ipa profile : 0.43 ( 0%) usr 0.05 ( 0%) sys 0.48 ( 0%) wall
0 kB ( 0%) ggc
ipa pure const : 3.00 ( 1%) usr 0.06 ( 0%) sys 3.07 ( 1%) wall
0 kB ( 0%) ggc
varconst : 0.03 ( 0%) usr 0.04 ( 0%) sys 0.06 ( 0%) wall
0 kB ( 0%) ggc
unaccounted todo : 0.48 ( 0%) usr 0.00 ( 0%) sys 0.50 ( 0%) wall
0 kB ( 0%) ggc
TOTAL : 236.22 15.50 252.15
6326146 kB
after:
Execution times (seconds)
phase setup : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 0%) wall
1399 kB ( 0%) ggc
phase opt and generate : 35.49 (28%) usr 0.44 ( 6%) sys 35.95 (26%) wall
313971 kB ( 5%) ggc
phase stream in : 82.98 (64%) usr 2.10 (30%) sys 85.13 (61%) wall
5969191 kB (95%) ggc
phase stream out : 10.37 ( 8%) usr 4.49 (64%) sys 17.33 (13%) wall
5813 kB ( 0%) ggc
garbage collection : 3.00 ( 2%) usr 0.00 ( 0%) sys 2.99 ( 2%) wall
0 kB ( 0%) ggc
callgraph optimization : 0.33 ( 0%) usr 0.00 ( 0%) sys 0.33 ( 0%) wall
30 kB ( 0%) ggc
ipa dead code removal : 4.91 ( 4%) usr 0.10 ( 1%) sys 5.04 ( 4%) wall
114 kB ( 0%) ggc
ipa inheritance graph : 0.10 ( 0%) usr 0.00 ( 0%) sys 0.10 ( 0%) wall
792 kB ( 0%) ggc
ipa virtual call target : 2.14 ( 2%) usr 0.01 ( 0%) sys 2.15 ( 2%) wall
21661 kB ( 0%) ggc
ipa cp : 2.34 ( 2%) usr 0.18 ( 3%) sys 2.52 ( 2%) wall
188629 kB ( 3%) ggc
ipa inlining heuristics : 18.43 (14%) usr 0.26 ( 4%) sys 18.68 (13%) wall
439993 kB ( 7%) ggc
ipa lto gimple in : 0.05 ( 0%) usr 0.05 ( 1%) sys 0.12 ( 0%) wall
0 kB ( 0%) ggc
ipa lto gimple out : 0.44 ( 0%) usr 0.06 ( 1%) sys 0.50 ( 0%) wall
0 kB ( 0%) ggc
ipa lto decl in : 69.27 (54%) usr 1.52 (22%) sys 70.87 (51%) wall
5180837 kB (82%) ggc
ipa lto decl out : 7.77 ( 6%) usr 0.51 ( 7%) sys 8.28 ( 6%) wall
0 kB ( 0%) ggc
ipa lto cgraph I/O : 1.71 ( 1%) usr 0.19 ( 3%) sys 1.90 ( 1%) wall
428974 kB ( 7%) ggc
ipa lto decl merge : 3.66 ( 3%) usr 0.00 ( 0%) sys 3.67 ( 3%) wall
8288 kB ( 0%) ggc
ipa lto cgraph merge : 3.40 ( 3%) usr 0.00 ( 0%) sys 3.39 ( 2%) wall
13725 kB ( 0%) ggc
whopr wpa : 3.19 ( 2%) usr 0.00 ( 0%) sys 3.19 ( 2%) wall
5816 kB ( 0%) ggc
whopr wpa I/O : 0.00 ( 0%) usr 3.92 (56%) sys 6.39 ( 5%) wall
0 kB ( 0%) ggc
whopr partitioning : 1.44 ( 1%) usr 0.02 ( 0%) sys 1.45 ( 1%) wall
0 kB ( 0%) ggc
ipa reference : 2.64 ( 2%) usr 0.08 ( 1%) sys 2.74 ( 2%) wall
0 kB ( 0%) ggc
ipa profile : 0.46 ( 0%) usr 0.02 ( 0%) sys 0.47 ( 0%) wall
0 kB ( 0%) ggc
ipa pure const : 3.02 ( 2%) usr 0.05 ( 1%) sys 3.08 ( 2%) wall
0 kB ( 0%) ggc
varconst : 0.06 ( 0%) usr 0.06 ( 1%) sys 0.07 ( 0%) wall
0 kB ( 0%) ggc
unaccounted todo : 0.48 ( 0%) usr 0.00 ( 0%) sys 0.48 ( 0%) wall
0 kB ( 0%) ggc
TOTAL : 128.85 7.05 138.45
6290376 kB
real 7m42.126s user 53m13.816s sys 2m16.993s
Seems almost like we are at level WPA does something useful. IPA inlining has
definitely room
for improvement. I think to significantly speedup LTO decl in, I think we need
to implement
Richard's original idea of compoaring the SCC in pickled version and
materializing only
theose that are unique.
Looks resonable?
Honza
* lto-cgraph.c (asm_nodes_output): Make global.
* lto-streamer.h (asm_nodes_output): Declare.
* lto-wrapper.c (parallel, jobserver): Make global.
(run_gcc): Pass down -fparallelism
* lto.c (lto_parallelism): New variable.
(do_stream_out): New function.
(stream_out): New function.
(lto_wpa_write_files): Use it.
* lang.opt (fparallelism): New.
* lto.h (lto_parallelism): Declare.
* lto-lang.c (lto_handle_option): Add fparalelism.
Index: lto-cgraph.c
===================================================================
--- lto-cgraph.c (revision 201891)
+++ lto-cgraph.c (working copy)
@@ -50,6 +50,9 @@ along with GCC; see the file COPYING3.
#include "context.h"
#include "pass_manager.h"
+/* True when asm nodes has been output. */
+bool asm_nodes_output = false;
+
static void output_cgraph_opt_summary (void);
static void input_cgraph_opt_summary (vec<symtab_node> nodes);
@@ -852,7 +855,6 @@ output_symtab (void)
lto_symtab_encoder_iterator lsei;
int i, n_nodes;
lto_symtab_encoder_t encoder;
- static bool asm_nodes_output = false;
if (flag_wpa)
output_cgraph_opt_summary ();
Index: lto-streamer.h
===================================================================
--- lto-streamer.h (revision 201891)
+++ lto-streamer.h (working copy)
@@ -870,6 +870,7 @@ void lto_output_location (struct output_
/* In lto-cgraph.c */
+extern bool asm_nodes_output;
lto_symtab_encoder_t lto_symtab_encoder_new (bool);
int lto_symtab_encoder_encode (lto_symtab_encoder_t, symtab_node);
void lto_symtab_encoder_delete (lto_symtab_encoder_t);
Index: lto-wrapper.c
===================================================================
--- lto-wrapper.c (revision 201891)
+++ lto-wrapper.c (working copy)
@@ -56,6 +56,9 @@ along with GCC; see the file COPYING3.
int debug; /* true if -save-temps. */
int verbose; /* true if -v. */
+int parallel = 0; /* number of parallel builds specified
+ by -flto=N */
+int jobserver = 0; /* true if -flto=jobserver was used. */
enum lto_mode_d {
LTO_MODE_NONE, /* Not doing LTO. */
@@ -445,8 +448,6 @@ run_gcc (unsigned argc, char *argv[])
char *list_option_full = NULL;
const char *linker_output = NULL;
const char *collect_gcc, *collect_gcc_options;
- int parallel = 0;
- int jobserver = 0;
bool no_partition = false;
struct cl_decoded_option *fdecoded_options = NULL;
unsigned int fdecoded_options_count = 0;
@@ -630,6 +631,16 @@ run_gcc (unsigned argc, char *argv[])
if (parallel <= 1)
parallel = 0;
}
+ if (jobserver)
+ {
+ obstack_ptr_grow (&argv_obstack, xstrdup
("-fparallelism=jobserver"));
+ }
+ else if (parallel > 1)
+ {
+ char buf[256];
+ sprintf (buf, "-fparallelism=%i", parallel);
+ obstack_ptr_grow (&argv_obstack, xstrdup (buf));
+ }
/* Fallthru. */
case OPT_flto:
Index: lto/lto.c
===================================================================
--- lto/lto.c (revision 201891)
+++ lto/lto.c (working copy)
@@ -49,6 +49,9 @@ along with GCC; see the file COPYING3.
#include "context.h"
#include "pass_manager.h"
+/* Number of parallel tasks to run, -1 if we want to use GNU Make jobserver.
*/
+int lto_parallelism;
+
static GTY(()) tree first_personality_decl;
/* Returns a hash code for P. */
@@ -3002,6 +3005,98 @@ cmp_partitions_order (const void *a, con
return orderb - ordera;
}
+/* Actually stream out ENCODER into TEMP_FILENAME. */
+
+void
+do_stream_out (char *temp_filename, lto_symtab_encoder_t encoder)
+{
+ lto_file *file = lto_obj_file_open (temp_filename, true);
+ if (!file)
+ fatal_error ("lto_obj_file_open() failed");
+ lto_set_current_out_file (file);
+
+ ipa_write_optimization_summaries (encoder);
+
+ lto_set_current_out_file (NULL);
+ lto_obj_file_close (file);
+ free (file);
+}
+
+/* Wait for forked process and signal errors. */
+#ifdef HAVE_WORKING_FORK
+void
+wait_for_child ()
+{
+ int status;
+ do
+ {
+ int w = waitpid(0, &status, WUNTRACED | WCONTINUED);
+ if (w == -1)
+ fatal_error ("waitpid failed");
+
+ if (WIFEXITED (status) && WEXITSTATUS (status))
+ fatal_error ("streaming subprocess failed");
+ else if (WIFSIGNALED (status))
+ fatal_error ("streaming subprocess was killed by signal");
+ }
+ while (!WIFEXITED(status) && !WIFSIGNALED(status));
+}
+#endif
+
+/* Stream out ENCODER into TEMP_FILENAME
+ Fork if that seems to help. */
+
+void
+stream_out (char *temp_filename, lto_symtab_encoder_t encoder, bool last)
+{
+#ifdef HAVE_WORKING_FORK
+ static int nruns;
+
+ if (!lto_parallelism || lto_parallelism == 1)
+ {
+ do_stream_out (temp_filename, encoder);
+ return;
+ }
+
+ /* Do not run more than LTO_PARALLELISM streamings
+ FIXME: we ignore limits on jobserver. */
+ if (lto_parallelism > 0 && nruns >= lto_parallelism)
+ {
+ wait_for_child ();
+ nruns --;
+ }
+ /* If this is not the last parallel partition, execute new
+ streaming process. */
+ if (!last)
+ {
+ pid_t cpid = fork ();
+
+ if (!cpid)
+ {
+ setproctitle ("lto1-wpa-streaming");
+ do_stream_out (temp_filename, encoder);
+ exit (0);
+ }
+ /* Fork failed; lets do the job ourseleves. */
+ else if (cpid == -1)
+ do_stream_out (temp_filename, encoder);
+ else
+ nruns++;
+ }
+ /* Last partition; stream it and wait for all children to die. */
+ else
+ {
+ int i;
+ do_stream_out (temp_filename, encoder);
+ for (i = 0; i < nruns; i++)
+ wait_for_child ();
+ }
+ asm_nodes_output = true;
+#else
+ do_stream_out (temp_filename, encoder);
+#endif
+}
+
/* Write all output files in WPA mode and the file with the list of
LTRANS units. */
@@ -3009,18 +3104,15 @@ static void
lto_wpa_write_files (void)
{
unsigned i, n_sets;
- lto_file *file;
ltrans_partition part;
FILE *ltrans_output_list_stream;
char *temp_filename;
+ vec <char *>temp_filenames = vNULL;
size_t blen;
/* Open the LTRANS output list. */
if (!ltrans_output_list)
fatal_error ("no LTRANS output list filename provided");
- ltrans_output_list_stream = fopen (ltrans_output_list, "w");
- if (ltrans_output_list_stream == NULL)
- fatal_error ("opening LTRANS output list %s: %m", ltrans_output_list);
timevar_push (TV_WHOPR_WPA);
@@ -3056,14 +3148,10 @@ lto_wpa_write_files (void)
: cmp_partitions_order);
for (i = 0; i < n_sets; i++)
{
- size_t len;
ltrans_partition part = ltrans_partitions[i];
/* Write all the nodes in SET. */
sprintf (temp_filename + blen, "%u.o", i);
- file = lto_obj_file_open (temp_filename, true);
- if (!file)
- fatal_error ("lto_obj_file_open() failed");
if (!quiet_flag)
fprintf (stderr, " %s (%s %i insns)", temp_filename, part->name,
part->insns);
@@ -3105,21 +3193,25 @@ lto_wpa_write_files (void)
}
gcc_checking_assert (lto_symtab_encoder_size (part->encoder) || !i);
- lto_set_current_out_file (file);
-
- ipa_write_optimization_summaries (part->encoder);
+ stream_out (temp_filename, part->encoder, i == n_sets - 1);
- lto_set_current_out_file (NULL);
- lto_obj_file_close (file);
- free (file);
part->encoder = NULL;
- len = strlen (temp_filename);
- if (fwrite (temp_filename, 1, len, ltrans_output_list_stream) < len
+ temp_filenames.safe_push (xstrdup (temp_filename));
+ }
+ ltrans_output_list_stream = fopen (ltrans_output_list, "w");
+ if (ltrans_output_list_stream == NULL)
+ fatal_error ("opening LTRANS output list %s: %m", ltrans_output_list);
+ for (i = 0; i < n_sets; i++)
+ {
+ unsigned int len = strlen (temp_filenames[i]);
+ if (fwrite (temp_filenames[i], 1, len, ltrans_output_list_stream) < len
|| fwrite ("\n", 1, 1, ltrans_output_list_stream) < 1)
fatal_error ("writing to LTRANS output list %s: %m",
ltrans_output_list);
+ free (temp_filenames[i]);
}
+ temp_filenames.release();
lto_stats.num_output_files += n_sets;
Index: lto/lang.opt
===================================================================
--- lto/lang.opt (revision 201891)
+++ lto/lang.opt (working copy)
@@ -32,6 +32,10 @@ fltrans-output-list=
LTO Joined Var(ltrans_output_list)
Specify a file to which a list of files output by LTRANS is written.
+fparallelism=
+LTO Joined
+Run the link-time optimizer in whole program analysis (WPA) mode.
+
fwpa
LTO Driver Report Var(flag_wpa)
Run the link-time optimizer in whole program analysis (WPA) mode.
Index: lto/lto.h
===================================================================
--- lto/lto.h (revision 201891)
+++ lto/lto.h (working copy)
@@ -39,6 +39,7 @@ extern const char *resolution_file_name;
extern tree lto_eh_personality (void);
extern void lto_main (void);
extern void lto_read_all_file_options (void);
+extern int lto_parallelism;
/* In lto-elf.c or lto-coff.c */
extern lto_file *lto_obj_file_open (const char *filename, bool writable);
Index: lto/lto-lang.c
===================================================================
--- lto/lto-lang.c (revision 201891)
+++ lto/lto-lang.c (working copy)
@@ -735,6 +735,19 @@ lto_handle_option (size_t scode, const c
warn_psabi = value;
break;
+ case OPT_fparallelism_:
+ if (!arg)
+ lto_parallelism = 1;
+ else if (!strcmp (arg, "jobserver"))
+ lto_parallelism = -1;
+ else
+ {
+ lto_parallelism = atoi (arg);
+ if (lto_parallelism <= 0)
+ lto_parallelism = 0;
+ }
+ break;
+
default:
break;
}
