http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60295
--- Comment #4 from Jan Hubicka <hubicka at ucw dot cz> --- > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60295 > > --- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> --- > lto_wpa_write_files has > > for (i = 0; i < n_sets; i++) > { > ... > stream_out (temp_filename, part->encoder, i == n_sets - 1); > ... > } > > n_sets is 32 when bootstrapping GCC. With parallel build, we > may build cc1, cc1plus, f951, cc1obj at the same time. If machine > is under heavy load, we may start 4*32 == 128 lto1-wpa-stream > processes at the same time with -flto=jobserver. This patch: > > diff --git a/gcc/lto/lto.c b/gcc/lto/lto.c > index c676d79..4023036 100644 > --- a/gcc/lto/lto.c > +++ b/gcc/lto/lto.c > @@ -3219,9 +3219,7 @@ do_whole_program_analysis (void) > lto_parallelism = 1; > > /* TODO: jobserver communicatoin is not supported, yet. */ > - if (!strcmp (flag_wpa, "jobserver")) > - lto_parallelism = -1; > - else > + if (strcmp (flag_wpa, "jobserver")) > { > lto_parallelism = atoi (flag_wpa); > if (lto_parallelism <= 0) > > limits lto1-wpa-stream process to 1 if -flto=jobserver is used. I think this is better variant $ svn diff ~/trunk/gcc/lto/lto.c Index: /aux/hubicka/trunk/gcc/lto/lto.c =================================================================== --- /aux/hubicka/trunk/gcc/lto/lto.c (revision 207702) +++ /aux/hubicka/trunk/gcc/lto/lto.c (working copy) @@ -2491,7 +2491,7 @@ stream_out (char *temp_filename, lto_sym #ifdef HAVE_WORKING_FORK static int nruns; - if (!lto_parallelism || lto_parallelism == 1) + if (lto_parallelism <= 1) { do_stream_out (temp_filename, encoder); return; I basically wanted to have simple jobserver client with lto_parallelism=-1, but I did not have time to implement it. (after glancing over GNU Make's implementation it seems actually bit non-trivial) I am adding Paul D. Smith into CC, since he wrote article on the implementation. Paul, we would like GCC to actually use jobserver to limit number of processes it forks internally for streaming. Is there an elegant and simple solution to get this implemented? I was thinking that if connecting to jobserver is hard, we can just produce makefile with rules waiting for read to finish and use it to get tokens into GCC streamer, but that seems somewhat kludgy. Jan
