From: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
Hi Jens,
This series adds __hot and __cold macros. Currently, the __hot macro
is not used. The __cold annotation hints the compiler to optimize for
code size. This is good for the slow-path in the setup.c file.
Here is the result compiling with Ubuntu clang
15.0.0-++20220601012204+ec2711b35411-1~exp1~20220601012300.510
Without this patchset:
$ wc -c src/liburing.so.2.3
71288 src/liburing.so.2.3
With this patchset:
$ wc -c src/liburing.so.2.3
69448 src/liburing.so.2.3
Take one slow-path function example, using __cold avoids aggresive
inlining.
Without this patchset:
00000000000024f0 <io_uring_queue_init>:
24f0: pushq %r14
24f2: pushq %rbx
24f3: subq $0x78,%rsp
24f7: movq %rsi,%r14
24fa: xorps %xmm0,%xmm0
24fd: movaps %xmm0,(%rsp)
2501: movaps %xmm0,0x60(%rsp)
2506: movaps %xmm0,0x50(%rsp)
250b: movaps %xmm0,0x40(%rsp)
2510: movaps %xmm0,0x30(%rsp)
2515: movaps %xmm0,0x20(%rsp)
251a: movaps %xmm0,0x10(%rsp)
251f: movq $0x0,0x70(%rsp)
2528: movl %edx,0x8(%rsp)
252c: movq %rsp,%rsi
252f: movl $0x1a9,%eax
2534: syscall
2536: movq %rax,%rbx
2539: testl %ebx,%ebx
253b: js 256a <io_uring_queue_init+0x7a>
253d: movq %rsp,%rsi
2540: movl %ebx,%edi
2542: movq %r14,%rdx
2545: callq 2080 <io_uring_queue_mmap@plt>
254a: testl %eax,%eax
254c: je 255d <io_uring_queue_init+0x6d>
254e: movl %eax,%edx
2550: movl $0x3,%eax
2555: movl %ebx,%edi
2557: syscall
2559: movl %edx,%ebx
255b: jmp 256a <io_uring_queue_init+0x7a>
255d: movl 0x14(%rsp),%eax
2561: movl %eax,0xc8(%r14)
2568: xorl %ebx,%ebx
256a: movl %ebx,%eax
256c: addq $0x78,%rsp
2570: popq %rbx
2571: popq %r14
2573: retq
With this patchset:
000000000000240c <io_uring_queue_init>:
240c: subq $0x78,%rsp
2410: xorps %xmm0,%xmm0
2413: movq %rsp,%rax
2416: movaps %xmm0,(%rax)
2419: movaps %xmm0,0x60(%rax)
241d: movaps %xmm0,0x50(%rax)
2421: movaps %xmm0,0x40(%rax)
2425: movaps %xmm0,0x30(%rax)
2429: movaps %xmm0,0x20(%rax)
242d: movaps %xmm0,0x10(%rax)
2431: movq $0x0,0x70(%rax)
2439: movl %edx,0x8(%rax)
243c: movq %rax,%rdx
243f: callq 2090 <io_uring_queue_init_params@plt>
2444: addq $0x78,%rsp
2448: retq
Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
---
Ammar Faizi (2):
lib: Add __hot and __cold macros
setup: Mark the exported functions as __cold
src/lib.h | 2 ++
src/setup.c | 25 ++++++++++++++-----------
2 files changed, 16 insertions(+), 11 deletions(-)
base-commit: 98c14a04e2c0dcdfbb71372a1a209ed889fb3e4d
--
Ammar Faizi
