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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 Thanks, Prathamesh > > Richard. > >> Thanks, >> Prathamesh >> > >> > Richard. >> > >> >> I have a silly question about partitioning: Does it hamper >> >> transformations on ipa optimizations if caller and >> >> callee get placed in separate partitions ? For instance if callee is >> >> supposed to be inlined >> >> into caller, would inlining still take place if callee and caller get >> >> placed in separate partitions ? >> >> I tried with a trivial example with -flto-partition=max >> >> which created 3 partitions for 3 functions (bar, foo and main), and it was >> >> able to inline bar into foo and foo into main. I am not sure how that happens. >> >> I thought ltrans can perform transformations on functions only within >> >> a single partition >> >> and not across partitions ? >> >> >> >> Thanks, >> >> Prathamesh >> >> > >> >> > Honza >> >> >> > >> > -- >> > Richard Biener <rguenther@suse.de> >> > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg) >> > > -- > Richard Biener <rguenther@suse.de> > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)
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