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.

1 files changed, 0 insertions, 35 deletions

diff --git a/bfd/linker.c b/bfd/linker.c
index 36cca9624c2..eb42a78b622 100644
--- a/bfd/linker.c
+++ b/bfd/linker.c
@@ -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;
-}