On 2021/5/17 10:42PM, Arnaldo Carvalho de Melo wrote:
Em Mon, May 17, 2021 at 08:06:30PM +0800, 程书意 escreveu:
To solve problems similar to _RH_KABI_REPLACE, _RH_KABI_REPLACE makes many
Can you explain what is _RH_KABI_REPLACE, why it is needed so that
people unfamiliar with it can make sense of your patch?
The _RH_KABI_REPLACE(_orig, _new) macros perserve size alignment and
kabi agreement between _orig and _new.Below is the definition of this macro:
# define _RH_KABI_REPLACE(_orig, _new) \
union { \
_new; \
struct { \
_orig; \
} __UNIQUE_ID(rh_kabi_hide); \
__RH_KABI_CHECK_SIZE_ALIGN(_orig, _new); \
}
__UNIQUE_ID uses the __COUNTER__ macro, and the __COUNTER__ macro is
automatically incremented by 1 every time it is precompiled. Therefore,
in different compilation units, the same structure has different
names.Here is a concrete example:
struct acpi_dev_node {
union {
struct acpi_device *companion;
struct {
void *handle;
} __UNIQUE_ID_rh_kabi_hide29;
union { };
};
};
struct acpi_dev_node {
union {
struct acpi_device *companion;
struct {
void *handle;
} __UNIQUE_ID_rh_kabi_hide31;
union { };
};
};
Finally, it will cause the btf algorithm to de-duplication efficiency is
not high, and time-consuming.
Also why "btf_prefix" when this is related to this other feature? Can
you find a better name?
"btf_prefix" means that if two strings have the same prefix, treat them
as the same string.From the above example,if btf_prefix is
__UNIQUE_ID_rh_kabi_hide, then __UNIQUE_ID_rh_kabi_hide29 and
__UNIQUE_ID_rh_kabi_hide31 are equal.Maybe "btf_kabi_prefix_string" is
better
You also forgot to update the man page at man-pages/pahole.1.
- Arnaldo
Yes i forgot.
structures have different names, resulting in a
particularly large vmlinux btf. For example, running ./pahole -J
vmlinux-3.10.0-1160.el7.x86_64 without --btf_prefix flag,
the running time is:
real 8m28.912s
user 8m27.271s
sys 0m1.471s
And the size of the generated btf segment is 30678240 bytes.
After adding the patch, running ./pahole
--btf_prefix=__UNIQUE_ID_rh_kabi_hide -J vmlinux-3.10.0-1160.el7.x86_64. The
running
time of the command is:
real 0m19.634s
user 0m18.457s
sys 0m1.169s
The size of the generated btf segment is 3117719 bytes.
Thanks.
Signed-off-by: chengshuyi<chengshuyi@xxxxxxxxxxxxxxxxx>
---
pahole.c | 10 ++++++++++
pahole_strings.h | 2 ++
strings.c | 9 +++++++--
3 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/pahole.c b/pahole.c
index dc40ccf..0b4f4ca 100644
--- a/pahole.c
+++ b/pahole.c
@@ -24,6 +24,7 @@
#include "btf_encoder.h"
#include "libbtf.h"
#include "lib/bpf/src/libbpf.h"
+#include "pahole_strings.h"
static bool btf_encode;
static bool ctf_encode;
@@ -855,6 +856,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
#define ARGP_btf_gen_floats 322
#define ARGP_btf_gen_all 323
#define ARGP_with_flexible_array 324
+#define ARGP_btf_prefix 325
static const struct argp_option pahole__options[] = {
{
@@ -1140,6 +1142,12 @@ static const struct argp_option pahole__options[] = {
.doc = "Path to the base BTF file",
},
{
+ .name = "btf_prefix",
+ .key = ARGP_btf_prefix,
+ .arg = "STRING",
+ .doc = "Strings with the same prefix are considered the same.",
+ },
+ {
.name = "btf_encode",
.key = 'J',
.doc = "Encode as BTF", @@ -1297,6 +1305,8 @@ static error_t pahole__options_parser(int
key, char *arg, btf_encode_force = true; break;
case ARGP_btf_base: base_btf_file = arg; break;
+ case ARGP_btf_prefix: + btf_prefix = arg; break;
case ARGP_numeric_version: print_numeric_version =
true; break; case ARGP_btf_gen_floats: diff --git
a/pahole_strings.h b/pahole_strings.h index 522fbf2..bf3dc7c 100644
--- a/pahole_strings.h +++ b/pahole_strings.h @@ -14,6 +14,8 @@
struct strings { struct btf *btf; }; +extern const char
*btf_prefix; + struct strings *strings__new(void); void
strings__delete(struct strings *strings); diff --git a/strings.c
b/strings.c index d37f49d..911ce25 100644 --- a/strings.c +++
b/strings.c @@ -16,6 +16,9 @@ #include "dutil.h"
#include "lib/bpf/src/libbpf.h"
+#include "libbtf.h"
Why do you need to add this new include? I guess you meant including
pahole_strings.h to get the forward declaration for 'btf_prefix'?
It is of no use, I forgot to delete it.
+
+const char *btf_prefix;
struct strings *strings__new(void)
{
@@ -47,8 +50,10 @@ strings_t strings__add(struct strings *strs, const char
*str)
if (str == NULL)
return 0;
-
- index = btf__add_str(strs->btf, str);
+ if(btf_prefix && strncmp(str,btf_prefix,strlen(btf_prefix))==0)
Please also follow the existing coding style, i.e. use a space after
'if' and also after the commas.
- Arnaldo
Okay, I know. If you want to receive this patch, I will send a complete
patch later.
+ index = btf__add_str(strs->btf, btf_prefix);
+ else
+ index = btf__add_str(strs->btf, str);
if (index < 0)
return 0;
--
1.8.3.1
