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elf: Don't cache symbol nor relocation tables with mmap 

During a "-j 8" LLVM 17 debug build on a machine with 32GB RAM and 16GB
swap, ld was killed by kernel because of out of memory:

[79437.949336] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0,global_oom,task_memcg=/user.slice/user-1000.slice/session-9.scope,task=ld,pid=797431,uid=1000
[79437.949349] Out of memory: Killed process 797431 (ld) total-vm:9219600kB, anon-rss:6558156kB, file-rss:1792kB, shmem-rss:0kB, UID:1000 pgtables:17552kB oom_score_adj:0

Don't cache symbol nor relocation tables if they are mapped in.  Data to
link the 3.5GB clang executable in LLVM 17 debug build on Linux/x86-64
with 32GB RAM is:

		stdio		mmap		improvement
user		86.73		87.02		-0.3%
system		9.55		9.21		3.6%
total		100.40		97.66		0.7%
maximum set(GB)	17.34		13.14		24%
page faults	4047667		3042877		25%

and data to link the 275M cc1plus executable in GCC 14 stage 1 build is:

user		5.41		5.44		-0.5%
system		0.80		0.76		5%
total		6.25		6.26		-0.2%
maximum set(MB)	1323		968		27%
page faults	323451		236371		27%

These improve the overall system performance for parallel build by
reducing memory usage and page faults.

Also rename _bfd_link_keep_memory to _bfd_elf_link_keep_memory.  Since
the --no-keep-memory linker option causes:

https://sourceware.org/bugzilla/show_bug.cgi?id=31458

this is opt-in by each backend.

bfd/

	* elf32-i386.c (elf_i386_scan_relocs): Remove
	_bfd_link_keep_memory.
	* elf64-x86-64.c (elf_x86_64_scan_relocs): Likewise.
	* elflink.c (_bfd_elf_link_keep_memory): New.
	(_bfd_elf_link_iterate_on_relocs): Replace _bfd_link_keep_memory
	with _bfd_elf_link_keep_memory.
	(elf_link_add_object_symbols): Likewise.
	(init_reloc_cookie): Likewise.
	(init_reloc_cookie_rels): Likewise.
	* libbfd-in.h (_bfd_link_keep_memory): Removed.
	* linker.c (_bfd_link_keep_memory): Likewise.
	* libbfd.h: Regenerated.
master
H.J. Lu 2 years ago
parent
c6291d749a
commit
d41b764855
6 changed files with 59 additions and 55 deletions
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  1. 2
      bfd/elf32-i386.c
  2. 2
      bfd/elf64-x86-64.c
  3. 69
      bfd/elflink.c
  4. 3
      bfd/libbfd-in.h
  5. 3
      bfd/libbfd.h
  6. 35
      bfd/linker.c

2
bfd/elf32-i386.c
View File

@ -1932,7 +1932,7 @@ elf_i386_scan_relocs (bfd *abfd,
if (elf_section_data (sec)->this_hdr.contents != contents)
{
if (!converted && !_bfd_link_keep_memory (info))
if (!converted)
_bfd_elf_munmap_section_contents (sec, contents);
else
{

2
bfd/elf64-x86-64.c
View File

@ -2590,7 +2590,7 @@ elf_x86_64_scan_relocs (bfd *abfd, struct bfd_link_info *info,
if (elf_section_data (sec)->this_hdr.contents != contents)
{
if (!converted && !_bfd_link_keep_memory (info))
if (!converted)
_bfd_elf_munmap_section_contents (sec, contents);
else
{

69
bfd/elflink.c
View File

@ -49,6 +49,53 @@ struct elf_info_failed
static bool _bfd_elf_fix_symbol_flags
(struct elf_link_hash_entry *, struct elf_info_failed *);
/* Return false if linker should avoid caching relocation information
and symbol tables of input files in memory. */
static bool
_bfd_elf_link_keep_memory (struct bfd_link_info *info)
{
#ifdef USE_MMAP
/* Don't cache symbol nor relocation tables if they are mapped in.
NB: Since the --no-keep-memory linker option causes:
https://sourceware.org/bugzilla/show_bug.cgi?id=31458
this is opt-in by each backend. */
const struct elf_backend_data *bed
= get_elf_backend_data (info->output_bfd);
if (bed->use_mmap)
return false;
#endif
bfd *abfd;
bfd_size_type size;
if (!info->keep_memory)
return false;
if (info->max_cache_size == (bfd_size_type) -1)
return true;
abfd = info->input_bfds;
size = info->cache_size;
do
{
if (size >= info->max_cache_size)
{
/* Over the limit. Reduce the memory usage. */
info->keep_memory = false;
return false;
}
if (!abfd)
break;
size += abfd->alloc_size;
abfd = abfd->link.next;
}
while (1);
return true;
}
asection *
_bfd_elf_section_for_symbol (struct elf_reloc_cookie *cookie,
unsigned long r_symndx,
@ -4182,10 +4229,9 @@ _bfd_elf_link_iterate_on_relocs
|| bfd_is_abs_section (o->output_section))
continue;
internal_relocs = _bfd_elf_link_info_read_relocs (abfd, info,
o, NULL,
NULL,
_bfd_link_keep_memory (info));
internal_relocs = _bfd_elf_link_info_read_relocs
(abfd, info, o, NULL, NULL,
_bfd_elf_link_keep_memory (info));
if (internal_relocs == NULL)
return false;
@ -5551,10 +5597,9 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
&& (s->flags & SEC_DEBUGGING) != 0))
continue;
internal_relocs = _bfd_elf_link_info_read_relocs (abfd, info,
s, NULL,
NULL,
_bfd_link_keep_memory (info));
internal_relocs = _bfd_elf_link_info_read_relocs
(abfd, info, s, NULL, NULL,
_bfd_elf_link_keep_memory (info));
if (internal_relocs == NULL)
goto error_free_vers;
@ -13616,7 +13661,7 @@ init_reloc_cookie (struct elf_reloc_cookie *cookie,
info->callbacks->einfo (_("%P%X: can not read symbols: %E\n"));
return false;
}
if (_bfd_link_keep_memory (info) )
if (_bfd_elf_link_keep_memory (info) )
{
symtab_hdr->contents = (bfd_byte *) cookie->locsyms;
info->cache_size += (cookie->locsymcount
@ -13653,9 +13698,9 @@ init_reloc_cookie_rels (struct elf_reloc_cookie *cookie,
}
else
{
cookie->rels = _bfd_elf_link_info_read_relocs (abfd, info, sec,
NULL, NULL,
_bfd_link_keep_memory (info));
cookie->rels = _bfd_elf_link_info_read_relocs
(abfd, info, sec, NULL, NULL,
_bfd_elf_link_keep_memory (info));
if (cookie->rels == NULL)
return false;
cookie->rel = cookie->rels;

3
bfd/libbfd-in.h
View File

@ -848,9 +848,6 @@ extern bfd_byte * _bfd_write_unsigned_leb128
extern struct bfd_link_info *_bfd_get_link_info (bfd *)
ATTRIBUTE_HIDDEN;
extern bool _bfd_link_keep_memory (struct bfd_link_info *)
ATTRIBUTE_HIDDEN;
extern uintptr_t _bfd_pagesize ATTRIBUTE_HIDDEN;
extern uintptr_t _bfd_pagesize_m1 ATTRIBUTE_HIDDEN;
extern uintptr_t _bfd_minimum_mmap_size ATTRIBUTE_HIDDEN;

3
bfd/libbfd.h
View File

@ -854,9 +854,6 @@ extern bfd_byte * _bfd_write_unsigned_leb128
extern struct bfd_link_info *_bfd_get_link_info (bfd *)
ATTRIBUTE_HIDDEN;
extern bool _bfd_link_keep_memory (struct bfd_link_info *)
ATTRIBUTE_HIDDEN;
extern uintptr_t _bfd_pagesize ATTRIBUTE_HIDDEN;
extern uintptr_t _bfd_pagesize_m1 ATTRIBUTE_HIDDEN;
extern uintptr_t _bfd_minimum_mmap_size ATTRIBUTE_HIDDEN;

35
bfd/linker.c
View File

@ -3556,38 +3556,3 @@ _bfd_nolink_bfd_define_start_stop (struct bfd_link_info *info ATTRIBUTE_UNUSED,
{
return (struct bfd_link_hash_entry *) _bfd_ptr_bfd_null_error (sec->owner);
}
/* Return false if linker should avoid caching relocation infomation
and symbol tables of input files in memory. */
bool
_bfd_link_keep_memory (struct bfd_link_info * info)
{
bfd *abfd;
bfd_size_type size;
if (!info->keep_memory)
return false;
if (info->max_cache_size == (bfd_size_type) -1)
return true;
abfd = info->input_bfds;
size = info->cache_size;
do
{
if (size >= info->max_cache_size)
{
/* Over the limit. Reduce the memory usage. */
info->keep_memory = false;
return false;
}
if (!abfd)
break;
size += abfd->alloc_size;
abfd = abfd->link.next;
}
while (1);
return true;
}

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