* [binutils-gdb] elf: Don't cache symbol nor relocation tables with mmap
@ 2024-04-03 16:17 H.J. Lu
0 siblings, 0 replies; only message in thread
From: H.J. Lu @ 2024-04-03 16:17 UTC (permalink / raw)
To: binutils-cvs
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d41b7648558757dbfd0958335dba1406be60fb4f
commit d41b7648558757dbfd0958335dba1406be60fb4f
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Wed Feb 28 14:34:33 2024 -0800
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.
Diff:
---
bfd/elf32-i386.c | 2 +-
bfd/elf64-x86-64.c | 2 +-
bfd/elflink.c | 69 ++++++++++++++++++++++++++++++++++++++++++++----------
bfd/libbfd-in.h | 3 ---
bfd/libbfd.h | 3 ---
bfd/linker.c | 35 ---------------------------
6 files changed, 59 insertions(+), 55 deletions(-)
diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index fa1846881d3..6183d962a83 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -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
{
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index ebfd455a822..60aa1802552 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -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
{
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 7e9f4c7f0b0..7a33da0a96c 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -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;
diff --git a/bfd/libbfd-in.h b/bfd/libbfd-in.h
index 889b221a950..7bfc58f12d8 100644
--- a/bfd/libbfd-in.h
+++ b/bfd/libbfd-in.h
@@ -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;
diff --git a/bfd/libbfd.h b/bfd/libbfd.h
index 0676f461382..bed7d88d4ec 100644
--- a/bfd/libbfd.h
+++ b/bfd/libbfd.h
@@ -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;
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;
-}
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2024-04-03 16:17 [binutils-gdb] elf: Don't cache symbol nor relocation tables with mmap H.J. Lu
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