On 6 April 2016 at 14:54, Richard Biener 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 wrote: >> > > On Wed, 6 Apr 2016, Prathamesh Kulkarni wrote: >> > > >> > >> On 5 April 2016 at 18:28, Richard Biener wrote: >> > >> > On Tue, 5 Apr 2016, Prathamesh Kulkarni wrote: >> > >> > >> > >> >> On 5 April 2016 at 16:58, Richard Biener wrote: >> > >> >> > On Tue, 5 Apr 2016, Prathamesh Kulkarni wrote: >> > >> >> > >> > >> >> >> On 4 April 2016 at 19:44, Jan Hubicka 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*-*-*. Thanks, Prathamesh > > Richard.