The patch titled
Subject: include/linux/unaligned: force inlining of byteswap operations
has been added to the -mm tree. Its filename is
force-inlining-of-unaligned-byteswap-operations.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/force-inlining-of-unaligned-byteswap-operations.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/force-inlining-of-unaligned-byteswap-operations.patch
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------------------------------------------------------
From: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Subject: include/linux/unaligned: force inlining of byteswap operations
Sometimes gcc mysteriously doesn't inline
very small functions we expect to be inlined. See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122
With this .config:
http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os,
the following functions get deinlined many times.
Examples of disassembly:
<get_unaligned_be16> (24 copies, 108 calls):
66 8b 07 mov (%rdi),%ax
55 push %rbp
48 89 e5 mov %rsp,%rbp
86 e0 xchg %ah,%al
5d pop %rbp
c3 retq
<get_unaligned_be32> (25 copies, 181 calls):
8b 07 mov (%rdi),%eax
55 push %rbp
48 89 e5 mov %rsp,%rbp
0f c8 bswap %eax
5d pop %rbp
c3 retq
<get_unaligned_be64> (23 copies, 94 calls):
48 8b 07 mov (%rdi),%rax
55 push %rbp
48 89 e5 mov %rsp,%rbp
48 0f c8 bswap %rax
5d pop %rbp
c3 retq
<put_unaligned_be16> (2 copies, 11 calls):
89 f8 mov %edi,%eax
55 push %rbp
c1 ef 08 shr $0x8,%edi
c1 e0 08 shl $0x8,%eax
09 c7 or %eax,%edi
48 89 e5 mov %rsp,%rbp
66 89 3e mov %di,(%rsi)
<put_unaligned_be32> (8 copies, 43 calls):
55 push %rbp
0f cf bswap %edi
89 3e mov %edi,(%rsi)
48 89 e5 mov %rsp,%rbp
5d pop %rbp
c3 retq
<put_unaligned_be64> (26 copies, 157 calls):
55 push %rbp
48 0f cf bswap %rdi
48 89 3e mov %rdi,(%rsi)
48 89 e5 mov %rsp,%rbp
5d pop %rbp
c3 retq
This patch fixes this via s/inline/__always_inline/.
It only affects arches with efficient unaligned access insns, such as x86.
(arched which lack such ops do not include linux/unaligned/access_ok.h)
Code size decrease after the patch is ~8.5k:
text data bss dec hex filename
92197848 20826112 36417536 149441496 8e84bd8 vmlinux
92189231 20826144 36417536 149432911 8e82a4f vmlinux6_unaligned_be_after
Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Graf <tgraf@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/unaligned/access_ok.h | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff -puN include/linux/unaligned/access_ok.h~force-inlining-of-unaligned-byteswap-operations include/linux/unaligned/access_ok.h
--- a/include/linux/unaligned/access_ok.h~force-inlining-of-unaligned-byteswap-operations
+++ a/include/linux/unaligned/access_ok.h
@@ -4,62 +4,62 @@
#include <linux/kernel.h>
#include <asm/byteorder.h>
-static inline u16 get_unaligned_le16(const void *p)
+static __always_inline u16 get_unaligned_le16(const void *p)
{
return le16_to_cpup((__le16 *)p);
}
-static inline u32 get_unaligned_le32(const void *p)
+static __always_inline u32 get_unaligned_le32(const void *p)
{
return le32_to_cpup((__le32 *)p);
}
-static inline u64 get_unaligned_le64(const void *p)
+static __always_inline u64 get_unaligned_le64(const void *p)
{
return le64_to_cpup((__le64 *)p);
}
-static inline u16 get_unaligned_be16(const void *p)
+static __always_inline u16 get_unaligned_be16(const void *p)
{
return be16_to_cpup((__be16 *)p);
}
-static inline u32 get_unaligned_be32(const void *p)
+static __always_inline u32 get_unaligned_be32(const void *p)
{
return be32_to_cpup((__be32 *)p);
}
-static inline u64 get_unaligned_be64(const void *p)
+static __always_inline u64 get_unaligned_be64(const void *p)
{
return be64_to_cpup((__be64 *)p);
}
-static inline void put_unaligned_le16(u16 val, void *p)
+static __always_inline void put_unaligned_le16(u16 val, void *p)
{
*((__le16 *)p) = cpu_to_le16(val);
}
-static inline void put_unaligned_le32(u32 val, void *p)
+static __always_inline void put_unaligned_le32(u32 val, void *p)
{
*((__le32 *)p) = cpu_to_le32(val);
}
-static inline void put_unaligned_le64(u64 val, void *p)
+static __always_inline void put_unaligned_le64(u64 val, void *p)
{
*((__le64 *)p) = cpu_to_le64(val);
}
-static inline void put_unaligned_be16(u16 val, void *p)
+static __always_inline void put_unaligned_be16(u16 val, void *p)
{
*((__be16 *)p) = cpu_to_be16(val);
}
-static inline void put_unaligned_be32(u32 val, void *p)
+static __always_inline void put_unaligned_be32(u32 val, void *p)
{
*((__be32 *)p) = cpu_to_be32(val);
}
-static inline void put_unaligned_be64(u64 val, void *p)
+static __always_inline void put_unaligned_be64(u64 val, void *p)
{
*((__be64 *)p) = cpu_to_be64(val);
}
_
Patches currently in -mm which might be from dvlasenk@xxxxxxxxxx are
asm-generic-force-inlining-of-some-atomic_long-operations.patch
force-inlining-of-some-byteswap-operations.patch
force-inlining-of-unaligned-byteswap-operations.patch
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