2022-12-27 16:18:18

by Thomas Weißschuh

Subject: [PATCH v2 3/8] objtool: allocate multiple structures with calloc()

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 <[email protected]>
---
tools/objtool/elf.c | 42 ++++++++++++++++++-------------------
tools/objtool/include/objtool/elf.h | 4 ++++
2 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 7eae95f33a72..9c326efb8cd9 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -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);
}
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index bb60fd42b46f..1c90f0ac0d53 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -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

--
2.39.0

2023-01-30 23:54:09

by Josh Poimboeuf

Subject: Re: [PATCH v2 3/8] objtool: allocate multiple structures with calloc()

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 :-)

--
Josh

2023-02-01 16:26:50

by tip-bot2 for Antonio Borneo

Subject: [tip: objtool/core] objtool: Allocate multiple structures with calloc()

The following commit has been merged into the objtool/core branch of tip:

Commit-ID: 389244804db54977b9316f0dc027ab69b3c1e8bf
Gitweb: https://git.kernel.org/tip/389244804db54977b9316f0dc027ab69b3c1e8bf
Author: Thomas Weißschuh <[email protected]>
AuthorDate: Tue, 27 Dec 2022 16:00:59
Committer: Josh Poimboeuf <[email protected]>
CommitterDate: Mon, 30 Jan 2023 16:28:19 -08:00

objtool: Allocate multiple structures with calloc()

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".

Note this introduces memory leaks, because some additional structs get
added to the lists later after reading the symbols and sections from the
original object. Luckily we don't really care about memory leaks in
objtool.

Signed-off-by: Thomas Weißschuh <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/elf.c | 42 ++++++++++++++--------------
tools/objtool/include/objtool/elf.h | 4 +++-
2 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 64443a7..6806ce0 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -284,13 +284,13 @@ 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);
@@ -422,13 +422,13 @@ 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;

@@ -918,13 +918,13 @@ 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))
@@ -1453,16 +1453,16 @@ 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);
}
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index bb60fd4..1c90f0a 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -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

2023-02-04 10:17:38

by tip-bot2 for Antonio Borneo

Subject: [tip: objtool/core] objtool: Allocate multiple structures with calloc()

The following commit has been merged into the objtool/core branch of tip:

Commit-ID: 8045b8f0b17edf375849f83c80dd05194850b6ed
Gitweb: https://git.kernel.org/tip/8045b8f0b17edf375849f83c80dd05194850b6ed
Author: Thomas Weißschuh <[email protected]>
AuthorDate: Tue, 27 Dec 2022 16:00:59
Committer: Josh Poimboeuf <[email protected]>
CommitterDate: Wed, 01 Feb 2023 09:15:23 -08:00

objtool: Allocate multiple structures with calloc()

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".

Note this introduces memory leaks, because some additional structs get
added to the lists later after reading the symbols and sections from the
original object. Luckily we don't really care about memory leaks in
objtool.

Signed-off-by: Thomas Weißschuh <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/elf.c | 42 ++++++++++++++--------------
tools/objtool/include/objtool/elf.h | 4 +++-
2 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 64443a7..6806ce0 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -284,13 +284,13 @@ 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);
@@ -422,13 +422,13 @@ 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;

@@ -918,13 +918,13 @@ 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))
@@ -1453,16 +1453,16 @@ 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);
}
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index bb60fd4..1c90f0a 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -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