[v2,3/8] objtool: allocate multiple structures with calloc()
Commit Message
By using calloc() instead of malloc() in a loop, libc does not have to
keep around bookkeeping information for each single structure.
This reduces maximum memory usage while processing vmlinux.o from
3153325 KB to 3035668 KB (-3.7%) on my notebooks "localmodconfig".
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
tools/objtool/elf.c | 42 ++++++++++++++++++-------------------
tools/objtool/include/objtool/elf.h | 4 ++++
2 files changed, 25 insertions(+), 21 deletions(-)
Comments
On Tue, Dec 27, 2022 at 04:00:59PM +0000, Thomas Weißschuh wrote:
> By using calloc() instead of malloc() in a loop, libc does not have to
> keep around bookkeeping information for each single structure.
If we cared about memory leaks, this wouldn't really work because some
structures are added in later, after the reading of the original
sections and symbols. Luckily we don't care :-)
@@ -285,13 +285,13 @@ static int read_sections(struct elf *elf)
!elf_alloc_hash(section_name, sections_nr))
return -1;
+ elf->section_data = calloc(sections_nr, sizeof(*sec));
+ if (!elf->section_data) {
+ perror("calloc");
+ return -1;
+ }
for (i = 0; i < sections_nr; i++) {
- sec = malloc(sizeof(*sec));
- if (!sec) {
- perror("malloc");
- return -1;
- }
- memset(sec, 0, sizeof(*sec));
+ sec = &elf->section_data[i];
INIT_LIST_HEAD(&sec->symbol_list);
INIT_LIST_HEAD(&sec->reloc_list);
@@ -423,13 +423,13 @@ static int read_symbols(struct elf *elf)
!elf_alloc_hash(symbol_name, symbols_nr))
return -1;
+ elf->symbol_data = calloc(symbols_nr, sizeof(*sym));
+ if (!elf->symbol_data) {
+ perror("calloc");
+ return -1;
+ }
for (i = 0; i < symbols_nr; i++) {
- sym = malloc(sizeof(*sym));
- if (!sym) {
- perror("malloc");
- return -1;
- }
- memset(sym, 0, sizeof(*sym));
+ sym = &elf->symbol_data[i];
sym->idx = i;
@@ -919,13 +919,13 @@ static int read_relocs(struct elf *elf)
sec->base->reloc = sec;
nr_reloc = 0;
+ sec->reloc_data = calloc(sec->sh.sh_size / sec->sh.sh_entsize, sizeof(*reloc));
+ if (!sec->reloc_data) {
+ perror("calloc");
+ return -1;
+ }
for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
- reloc = malloc(sizeof(*reloc));
- if (!reloc) {
- perror("malloc");
- return -1;
- }
- memset(reloc, 0, sizeof(*reloc));
+ reloc = &sec->reloc_data[i];
switch (sec->sh.sh_type) {
case SHT_REL:
if (read_rel_reloc(sec, i, reloc, &symndx))
@@ -1458,16 +1458,16 @@ void elf_close(struct elf *elf)
list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
list_del(&sym->list);
hash_del(&sym->hash);
- free(sym);
}
list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) {
list_del(&reloc->list);
hash_del(&reloc->hash);
- free(reloc);
}
list_del(&sec->list);
- free(sec);
+ free(sec->reloc_data);
}
+ free(elf->symbol_data);
+ free(elf->section_data);
free(elf);
}
@@ -39,6 +39,7 @@ struct section {
char *name;
int idx;
bool changed, text, rodata, noinstr, init, truncate;
+ struct reloc *reloc_data;
};
struct symbol {
@@ -104,6 +105,9 @@ struct elf {
struct hlist_head *section_hash;
struct hlist_head *section_name_hash;
struct hlist_head *reloc_hash;
+
+ struct section *section_data;
+ struct symbol *symbol_data;
};
#define OFFSET_STRIDE_BITS 4