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.
Is it OK after bootstrap+test ?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)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 9e54bb7..f0de7ec 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..d385dd9 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, bool honor_max_partition)
{
int n_nodes = 0;
int n_varpool_nodes = 0, varpool_pos = 0, best_varpool_pos = 0;
@@ -511,9 +511,13 @@ 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);
+
npartitions = 1;
partition = new_partition ("");
if (symtab->dump_file)
@@ -719,7 +723,9 @@ 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
+ || (honor_max_partition
+ && partition->insns > PARAM_VALUE (MAX_PARTITION_SIZE)))
{
if (best_i != i)
{
diff --git a/gcc/lto/lto-partition.h b/gcc/lto/lto-partition.h
index 31e3764..2992bee 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, bool honor_max_partition = true);
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..82bd9b3 100644
--- a/gcc/lto/lto.c
+++ b/gcc/lto/lto.c
@@ -3112,12 +3112,13 @@ do_whole_program_analysis (void)
timevar_pop (TV_WHOPR_WPA);
timevar_push (TV_WHOPR_PARTITIONING);
+
if (flag_lto_partition == LTO_PARTITION_1TO1)
lto_1_to_1_map ();
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, false);
else if (flag_lto_partition == LTO_PARTITION_BALANCED)
lto_balanced_map (PARAM_VALUE (PARAM_LTO_PARTITIONS));
else
diff --git a/gcc/params.def b/gcc/params.def
index 9362c15..97e41aa 100644
--- a/gcc/params.def
+++ b/gcc/params.def
@@ -1027,7 +1027,12 @@ DEFPARAM (PARAM_LTO_PARTITIONS,
DEFPARAM (MIN_PARTITION_SIZE,
"lto-min-partition",
"Minimal size of a partition for LTO (in estimated instructions).",
- 1000, 0, 0)
+ 10000, 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. */
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