On 6 April 2016 at 13:44, Richard Biener <rguent...@suse.de> wrote:
> 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?
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.Thanks, Prathamesh > > 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)
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..bd6dc1e 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 +723,8 @@ 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..b0b533b 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..7663a5b 100644
--- a/gcc/lto/lto.c
+++ b/gcc/lto/lto.c
@@ -3117,9 +3118,10 @@ 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 9362c15..b5da384 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,
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