On Wed, 6 Apr 2016, Prathamesh Kulkarni wrote: > On 5 April 2016 at 18:28, Richard Biener <rguent...@suse.de> wrote: > > On Tue, 5 Apr 2016, Prathamesh Kulkarni wrote: > > > >> On 5 April 2016 at 16:58, Richard Biener <rguent...@suse.de> wrote: > >> > On Tue, 5 Apr 2016, Prathamesh Kulkarni wrote: > >> > > >> >> On 4 April 2016 at 19:44, Jan Hubicka <hubi...@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? Richard. > 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 <rguent...@suse.de> > >> > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, > >> > HRB 21284 (AG Nuernberg) > >> > > > > -- > > Richard Biener <rguent...@suse.de> > > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB > > 21284 (AG Nuernberg) > -- Richard Biener <rguent...@suse.de> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)