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Re: PATCH: Use a hash table for 26X linker speedup
- From: Christian Joensson <christian dot joensson at gmail dot com>
- To: "H. J. Lu" <hjl at lucon dot org>
- Cc: binutils at sources dot redhat dot com
- Date: Sat, 21 May 2005 08:40:55 +0200
- Subject: Re: PATCH: Use a hash table for 26X linker speedup
- References: <20050501165707.GA13713@lucon.org> <20050501190856.GA15653@lucon.org>
- Reply-to: Christian Joensson <christian dot joensson at gmail dot com>
Whatever happened with this?
/ChJ
On 5/1/05, H. J. Lu <hjl@lucon.org> wrote:
> On Sun, May 01, 2005 at 09:57:07AM -0700, H. J. Lu wrote:
> > Linker is very slow on input files with many sections. The 64k section
> > test is only enabled for CRIS. I did a profile. 70% of linker time is
> > spent in lang_check_section_addresses:
> >
> > Flat profile:
> >
> > Each sample counts as 0.01 seconds.
> > % cumulative self self total
> > time seconds seconds calls Ks/call Ks/call name
> > 72.92 948.31 948.31 1 0.95 0.95 lang_check_section_addresses
> > 22.37 1239.21 290.90 132089 0.00 0.00 lang_output_section_find_1
> >
> > The main problem is we use a single section list. We have to scan the
> > whole list for anything. In case of address overlap check, we only
> > need to check the previous section. There are many other places in
> > bfd, assembler and linker where a double section list will help. With
> > this patch, I got 30% linker speed up in 64k section test:
> >
> > The old linker:
> >
> > sh 1 502.74s user 0.90s system 99% cpu 8:23.73 total
> >
> > The new linker:
> >
> > sh 1 340.58s user 0.90s system 99% cpu 5:41.55 total
> >
> > The profile data shows:
> >
> > Flat profile:
> >
> > Each sample counts as 0.01 seconds.
> > % cumulative self self total
> > time seconds seconds calls s/call s/call name
> > 81.20 256.42 256.42 132089 0.00 0.00 lang_output_section_find_1
> > 13.27 298.33 41.91 673985 0.00 0.00 bfd_hash_lookup
> >
> > I will work on lang_output_section_find_1 next. I am planning to use
> > a hash table. I hope to enable 64k section on all ELF targets.
> >
>
> This is the patch. I got
>
> sh 1 13.39s user 1.28s system 95% cpu 15.431 total
>
> vs.
>
> sh 1 340.58s user 0.90s system 99% cpu 5:41.55 total
>
> That is a 26X speed up. I enabled 64k section test for all ELF targets.
>
>
> H.J.
> ----
> ld/
>
> 2005-05-01 H.J. Lu <hongjiu.lu@intel.com>
>
> * ldlang.c (output_statement_hash_entry): New type.
> (output_statement_table): New variable for hash table.
> (output_statement_newfunc): New function.
> (output_statement_table_init): Likewise.
> (output_statement_table_free): Likewise.
> (lang_init): Call output_statement_table_init.
> (lang_finish): Renamed to ...
> (lang_end): This.
> (lang_process): Updated.
> (lang_finish): New function.
> (lang_output_section_find_1): Use hash table.
> (lang_output_section_statement_lookup_1): Likewise.
>
> * ldlang.h (lang_finish): New.
>
> * ldmain.c (main): Call lang_finish.
>
> ld/testsuite/
>
> 2005-05-01 H.J. Lu <hongjiu.lu@intel.com>
>
> * ld-elf/sec64k.exp: Enabled for all ELF targets.
>
> --- ld/ldlang.c.hash 2005-05-01 09:00:10.000000000 -0700
> +++ ld/ldlang.c 2005-05-01 12:05:32.000000000 -0700
> @@ -863,6 +863,45 @@ lang_add_input_file (const char *name,
> return new_afile (name, file_type, target, TRUE);
> }
>
> +struct output_statement_hash_entry
> +{
> + struct bfd_hash_entry root;
> + lang_output_section_statement_type *entry;
> +};
> +
> +/* The hash table. */
> +
> +static struct bfd_hash_table output_statement_table;
> +
> +/* Support routines for the hash table used by lang_output_section_find_1,
> + initialize the table, fill in an entry and remove the table. */
> +
> +static struct bfd_hash_entry *
> +output_statement_newfunc (struct bfd_hash_entry *entry ATTRIBUTE_UNUSED,
> + struct bfd_hash_table *table,
> + const char *string ATTRIBUTE_UNUSED)
> +{
> + struct output_statement_hash_entry *ret
> + = bfd_hash_allocate (table,
> + sizeof (struct output_statement_hash_entry));
> + ret->entry = NULL;
> + return (struct bfd_hash_entry *) ret;
> +}
> +
> +static void
> +output_statement_table_init (void)
> +{
> + if (! bfd_hash_table_init_n (&output_statement_table,
> + output_statement_newfunc, 61))
> + einfo (_("%P%F: Failed to create hash table\n"));
> +}
> +
> +static void
> +output_statement_table_free (void)
> +{
> + bfd_hash_table_free (&output_statement_table);
> +}
> +
> /* Build enough state so that the parser can build its tree. */
>
> void
> @@ -872,6 +911,8 @@ lang_init (void)
>
> stat_ptr = &statement_list;
>
> + output_statement_table_init ();
> +
> lang_list_init (stat_ptr);
>
> lang_list_init (&input_file_chain);
> @@ -898,6 +939,12 @@ lang_init (void)
> lang_statement_iteration = 0;
> }
>
> +void
> +lang_finish (void)
> +{
> + output_statement_table_free ();
> +}
> +
> /*----------------------------------------------------------------------
> A region is an area of memory declared with the
> MEMORY { name:org=exp, len=exp ... }
> @@ -983,16 +1030,28 @@ static lang_output_section_statement_typ
> lang_output_section_find_1 (const char *const name, int constraint)
> {
> lang_output_section_statement_type *lookup;
> + struct output_statement_hash_entry *entry;
> + unsigned long hash;
>
> - for (lookup = &lang_output_section_statement.head->output_section_statement;
> - lookup != NULL;
> - lookup = lookup->next)
> + entry = ((struct output_statement_hash_entry *)
> + bfd_hash_lookup (&output_statement_table, name, FALSE,
> + FALSE));
> + if (entry == NULL || (lookup = entry->entry) == NULL)
> + return NULL;
> +
> + hash = entry->root.hash;
> + do
> {
> - if (strcmp (name, lookup->name) == 0
> - && lookup->constraint != -1
> + if (lookup->constraint != -1
> && (constraint == 0 || constraint == lookup->constraint))
> return lookup;
> + entry = (struct output_statement_hash_entry *) entry->root.next;
> + lookup = entry ? entry->entry : NULL;
> }
> + while (entry != NULL
> + && entry->root.hash == hash
> + && strcmp (name, lookup->name) == 0);
> +
> return NULL;
> }
>
> @@ -1010,6 +1069,8 @@ lang_output_section_statement_lookup_1 (
> lookup = lang_output_section_find_1 (name, constraint);
> if (lookup == NULL)
> {
> + struct output_statement_hash_entry *entry;
> +
> lookup = new_stat (lang_output_section_statement, stat_ptr);
> lookup->region = NULL;
> lookup->lma_region = NULL;
> @@ -1034,6 +1095,15 @@ lang_output_section_statement_lookup_1 (
> lookup->update_dot_tree = NULL;
> lookup->phdrs = NULL;
>
> + entry = ((struct output_statement_hash_entry *)
> + bfd_hash_lookup (&output_statement_table, name, TRUE,
> + FALSE));
> + if (entry == NULL)
> + einfo (_("%P%F: bfd_hash_lookup failed creating section `%s'\n"),
> + name);
> +
> + entry->entry = lookup;
> +
> lang_statement_append (&lang_output_section_statement,
> (lang_statement_union_type *) lookup,
> (lang_statement_union_type **) &lookup->next);
> @@ -4495,7 +4565,7 @@ lang_set_startof (void)
> }
>
> static void
> -lang_finish (void)
> +lang_end (void)
> {
> struct bfd_link_hash_entry *h;
> bfd_boolean warn;
> @@ -5294,7 +5364,7 @@ lang_process (void)
> /* Final stuffs. */
>
> ldemul_finish ();
> - lang_finish ();
> + lang_end ();
> }
>
> /* EXPORTED TO YACC */
> --- ld/ldlang.h.hash 2005-05-01 09:00:10.000000000 -0700
> +++ ld/ldlang.h 2005-05-01 11:39:36.000000000 -0700
> @@ -449,6 +449,8 @@ extern int lang_statement_iteration;
>
> extern void lang_init
> (void);
> +extern void lang_finish
> + (void);
> extern lang_memory_region_type *lang_memory_region_lookup
> (const char *const, bfd_boolean);
> extern lang_memory_region_type *lang_memory_region_default
> --- ld/ldmain.c.hash 2005-03-16 17:37:00.000000000 -0800
> +++ ld/ldmain.c 2005-05-01 11:40:39.000000000 -0700
> @@ -474,6 +474,8 @@ main (int argc, char **argv)
> if (nocrossref_list != NULL)
> check_nocrossrefs ();
>
> + lang_finish ();
> +
> /* Even if we're producing relocatable output, some non-fatal errors should
> be reported in the exit status. (What non-fatal errors, if any, do we
> want to ignore for relocatable output?) */
> --- ld/testsuite/ld-elf/sec64k.exp.hash 2005-03-03 08:56:35.000000000 -0800
> +++ ld/testsuite/ld-elf/sec64k.exp 2005-05-01 11:50:34.000000000 -0700
> @@ -24,12 +24,6 @@ if ![is_elf_format] {
> return
> }
>
> -# Per-port excludes, since this test takes an overwhelmingly long time
> -# currently.
> -if { ![istarget cris-*-*] } {
> - return
> -}
> -
> # Test >64k sections, with and without -r. First, create the assembly
> # files. Have a relocation to another section and one within the local
> # section.
>
--
Cheers,
/ChJ