| Message ID | CAAgBjMnGYAHhdsEsyHuEExwsjeF+qN6o=A_fP042198F9H6_DA@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On 26 April 2016 at 16:31, Richard Biener <rguenther@suse.de> wrote: > On Mon, 25 Apr 2016, Prathamesh Kulkarni wrote: > >> On 6 April 2016 at 14:54, Richard Biener <rguenther@suse.de> wrote: >> > On Wed, 6 Apr 2016, Richard Biener wrote: >> > >> >> On Wed, 6 Apr 2016, Prathamesh Kulkarni wrote: >> >> >> >> > On 6 April 2016 at 13:44, Richard Biener <rguenther@suse.de> wrote: >> >> > > On Wed, 6 Apr 2016, Prathamesh Kulkarni wrote: >> >> > > >> >> > >> On 5 April 2016 at 18:28, Richard Biener <rguenther@suse.de> wrote: >> >> > >> > On Tue, 5 Apr 2016, Prathamesh Kulkarni wrote: >> >> > >> > >> >> > >> >> On 5 April 2016 at 16:58, Richard Biener <rguenther@suse.de> wrote: >> >> > >> >> > On Tue, 5 Apr 2016, Prathamesh Kulkarni wrote: >> >> > >> >> > >> >> > >> >> >> On 4 April 2016 at 19:44, Jan Hubicka <hubicka@ucw.cz> wrote: >> >> > >> >> >> > >> >> > >> >> >> >> diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c >> >> > >> >> >> >> index 9eb63c2..bc0c612 100644 >> >> > >> >> >> >> --- a/gcc/lto/lto-partition.c >> >> > >> >> >> >> +++ b/gcc/lto/lto-partition.c >> >> > >> >> >> >> @@ -511,9 +511,20 @@ lto_balanced_map (int n_lto_partitions) >> >> > >> >> >> >> varpool_order.qsort (varpool_node_cmp); >> >> > >> >> >> >> >> >> > >> >> >> >> /* Compute partition size and create the first partition. */ >> >> > >> >> >> >> + if (PARAM_VALUE (MIN_PARTITION_SIZE) > PARAM_VALUE (MAX_PARTITION_SIZE)) >> >> > >> >> >> >> + fatal_error (input_location, "min partition size cannot be greater than max partition size"); >> >> > >> >> >> >> + >> >> > >> >> >> >> partition_size = total_size / n_lto_partitions; >> >> > >> >> >> >> if (partition_size < PARAM_VALUE (MIN_PARTITION_SIZE)) >> >> > >> >> >> >> partition_size = PARAM_VALUE (MIN_PARTITION_SIZE); >> >> > >> >> >> >> + else if (partition_size > PARAM_VALUE (MAX_PARTITION_SIZE)) >> >> > >> >> >> >> + { >> >> > >> >> >> >> + n_lto_partitions = total_size / PARAM_VALUE (MAX_PARTITION_SIZE); >> >> > >> >> >> >> + if (total_size % PARAM_VALUE (MAX_PARTITION_SIZE)) >> >> > >> >> >> >> + n_lto_partitions++; >> >> > >> >> >> >> + partition_size = total_size / n_lto_partitions; >> >> > >> >> >> >> + } >> >> > >> >> >> > >> >> > >> >> >> > lto_balanced_map actually works in a way that looks for cheapest cutpoint in range >> >> > >> >> >> > 3/4*parittion_size to 2*partition_size and picks the cheapest range. >> >> > >> >> >> > Setting partition_size to this value will thus not cause partitioner to produce smaller >> >> > >> >> >> > partitions only. I suppose modify the conditional: >> >> > >> >> >> > >> >> > >> >> >> > /* Partition is too large, unwind into step when best cost was reached and >> >> > >> >> >> > start new partition. */ >> >> > >> >> >> > if (partition->insns > 2 * partition_size) >> >> > >> >> >> > >> >> > >> >> >> > and/or in the code above set the partition_size to half of total_size/max_size. >> >> > >> >> >> > >> >> > >> >> >> > I know this is somewhat sloppy. This was really just first cut implementation >> >> > >> >> >> > many years ago. I expected to reimplement it marter soon, but then there was >> >> > >> >> >> > never really a need for it (I am trying to avoid late IPA optimizations so the >> >> > >> >> >> > partitioning decisions should mostly affect compile time performance only). >> >> > >> >> >> > If ARM is more sensitive for partitining, perhaps it would make sense to try to >> >> > >> >> >> > look for something smarter. >> >> > >> >> >> > >> >> > >> >> >> >> + >> >> > >> >> >> >> npartitions = 1; >> >> > >> >> >> >> partition = new_partition (""); >> >> > >> >> >> >> if (symtab->dump_file) >> >> > >> >> >> >> diff --git a/gcc/lto/lto.c b/gcc/lto/lto.c >> >> > >> >> >> >> index 9dd513f..294b8a4 100644 >> >> > >> >> >> >> --- a/gcc/lto/lto.c >> >> > >> >> >> >> +++ b/gcc/lto/lto.c >> >> > >> >> >> >> @@ -3112,6 +3112,12 @@ do_whole_program_analysis (void) >> >> > >> >> >> >> timevar_pop (TV_WHOPR_WPA); >> >> > >> >> >> >> >> >> > >> >> >> >> timevar_push (TV_WHOPR_PARTITIONING); >> >> > >> >> >> >> + >> >> > >> >> >> >> + if (flag_lto_partition != LTO_PARTITION_BALANCED >> >> > >> >> >> >> + && PARAM_VALUE (MAX_PARTITION_SIZE) != INT_MAX) >> >> > >> >> >> >> + fatal_error (input_location, "--param max-lto-partition should only" >> >> > >> >> >> >> + " be used with balanced partitioning\n"); >> >> > >> >> >> >> + >> >> > >> >> >> > >> >> > >> >> >> > I think we should wire in resonable MAX_PARTITION_SIZE default. THe value you >> >> > >> >> >> > found experimentally may be a good start. For that reason we can't really >> >> > >> >> >> > refuse a value when !LTO_PARTITION_BALANCED. Just document it as parameter for >> >> > >> >> >> > balanced partitioning only and add a parameter to lto_balanced_map specifying whether >> >> > >> >> >> > this param should be honored (because the same path is used for partitioning to one partition) >> >> > >> >> >> > >> >> > >> >> >> > Otherwise the patch looks good to me modulo missing documentation. >> >> > >> >> >> Thanks for the review. I have updated the patch. >> >> > >> >> >> Does this version look OK ? >> >> > >> >> >> I had randomly chosen 10000, not sure if that's an appropriate value >> >> > >> >> >> for default. >> >> > >> >> > >> >> > >> >> > I think it's way too small. This is roughly the number of GIMPLE stmts >> >> > >> >> > (thus roughly the number of instructions). So with say a 8 byte >> >> > >> >> > instruction format it is on the order of 80kB. You'd want to have a >> >> > >> >> > default of at least several ten times of large-unit-insns (also 10000). >> >> > >> >> > I'd choose sth like 1000000 (one million). I find the lto-min-partition >> >> > >> >> > number quite small as well (and up it by a factor of 10). >> >> > >> >> Done in this version. >> >> > >> > >> >> > >> > I'd do that separately. >> >> > >> > >> >> > >> > Please no default parameter for lto_balanced_map (), instead change >> >> > >> > all callers. >> >> > >> > >> >> > >> >> Is it OK after bootstrap+test ? >> >> > >> > >> >> > >> > Note that this is for stage1 only. I'll leave approval to Honza >> >> > >> > (also verification of the default max param - not sure if for example >> >> > >> > chromium or firefox should/will be split to more than 32 partitions >> >> > >> > with the patch) >> >> > >> Removed default parameter in this version. I verified with the patch >> >> > >> for chromium LTO build: >> >> > >> n_lto_partitions == 32, ltrans_partitions.length() == 31 >> >> > > >> >> > > Just noticed that lto_balanced_map already gets PARAM_LTO_PARTITIONS, >> >> > > so why not pass it PARAM_MAX_PARTITION_SIZE or 0 (as magic value for >> >> > > unlimited) instead of a bool parameter? >> >> > Indeed. Instead of 0, would it be OK to pass INT_MAX as 2nd parameter in case >> >> > of single partition, since in that case partition->insns > >> >> > max_partition_size will never >> >> > be true, which would effectively ignore max_partition_size. >> >> >> >> You mean we are limited to INT_MAX partition size anyway, even on 64bit >> >> systems? ... (but yes, using a suitable large number works as well) >> > >> > Ah, even 'total_size' is an int ... I wonder what this means for LTOing >> > a -mcmodel=large app (that really needs the large model). >> Hi, >> Is the attached patch OK for trunk now ? >> Bootstrapped and tested on x86_64-unknown-linux-gnu. >> Cross tested on arm*-*-* and aarch64*-*-*. > > Ok. How many partitions do we generate for linking cc1 with > bootstrap-lto now? No difference with patch in number of partitions: ltrans_partitions.length() == 31, n_lto_partitions == 32. Should I commit it ? Thanks, Prathamesh > > Thanks, > Richard.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 821f8fd..4afa32c 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -9477,6 +9477,11 @@ Size of minimal partition for WHOPR (in estimated instructions). This prevents expenses of splitting very small programs into too many partitions. +@item lto-max-partition +Size of max partition for WHOPR (in estimated instructions). +to provide an upper bound for individual size of partition. +Meant to be used only with balanced partitioning. + @item cxx-max-namespaces-for-diagnostic-help The maximum number of namespaces to consult for suggestions when C++ name lookup fails for an identifier. The default is 1000. diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c index 9eb63c2..c191d24 100644 --- a/gcc/lto/lto-partition.c +++ b/gcc/lto/lto-partition.c @@ -447,7 +447,7 @@ add_sorted_nodes (vec<symtab_node *> &next_nodes, ltrans_partition partition) and in-partition calls was reached. */ void -lto_balanced_map (int n_lto_partitions) +lto_balanced_map (int n_lto_partitions, int max_partition_size) { int n_nodes = 0; int n_varpool_nodes = 0, varpool_pos = 0, best_varpool_pos = 0; @@ -511,6 +511,9 @@ lto_balanced_map (int n_lto_partitions) varpool_order.qsort (varpool_node_cmp); /* Compute partition size and create the first partition. */ + if (PARAM_VALUE (MIN_PARTITION_SIZE) > max_partition_size) + fatal_error (input_location, "min partition size cannot be greater than max partition size"); + partition_size = total_size / n_lto_partitions; if (partition_size < PARAM_VALUE (MIN_PARTITION_SIZE)) partition_size = PARAM_VALUE (MIN_PARTITION_SIZE); @@ -719,7 +722,8 @@ lto_balanced_map (int n_lto_partitions) best_cost, best_internal, best_i); /* Partition is too large, unwind into step when best cost was reached and start new partition. */ - if (partition->insns > 2 * partition_size) + if (partition->insns > 2 * partition_size + || partition->insns > max_partition_size) { if (best_i != i) { diff --git a/gcc/lto/lto-partition.h b/gcc/lto/lto-partition.h index 31e3764..f7abe62 100644 --- a/gcc/lto/lto-partition.h +++ b/gcc/lto/lto-partition.h @@ -35,7 +35,7 @@ extern vec<ltrans_partition> ltrans_partitions; void lto_1_to_1_map (void); void lto_max_map (void); -void lto_balanced_map (int); +void lto_balanced_map (int, int); void lto_promote_cross_file_statics (void); void free_ltrans_partitions (void); void lto_promote_statics_nonwpa (void); diff --git a/gcc/lto/lto.c b/gcc/lto/lto.c index 9dd513f..af735cb 100644 --- a/gcc/lto/lto.c +++ b/gcc/lto/lto.c @@ -3117,9 +3117,10 @@ do_whole_program_analysis (void) else if (flag_lto_partition == LTO_PARTITION_MAX) lto_max_map (); else if (flag_lto_partition == LTO_PARTITION_ONE) - lto_balanced_map (1); + lto_balanced_map (1, INT_MAX); else if (flag_lto_partition == LTO_PARTITION_BALANCED) - lto_balanced_map (PARAM_VALUE (PARAM_LTO_PARTITIONS)); + lto_balanced_map (PARAM_VALUE (PARAM_LTO_PARTITIONS), + PARAM_VALUE (MAX_PARTITION_SIZE)); else gcc_unreachable (); diff --git a/gcc/params.def b/gcc/params.def index dbff305..eceee32 100644 --- a/gcc/params.def +++ b/gcc/params.def @@ -1029,6 +1029,11 @@ DEFPARAM (MIN_PARTITION_SIZE, "Minimal size of a partition for LTO (in estimated instructions).", 1000, 0, 0) +DEFPARAM (MAX_PARTITION_SIZE, + "lto-max-partition", + "Maximal size of a partition for LTO (in estimated instructions).", + 1000000, 0, INT_MAX) + /* Diagnostic parameters. */ DEFPARAM (CXX_MAX_NAMESPACES_FOR_DIAGNOSTIC_HELP,