From: Bart Van Assche <bvanassche@acm.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: io-uring@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>
Subject: [PATCH liburing 3/3] Convert __io_uring_get_sqe() from a macro into an inline function
Date: Sun, 21 Jun 2020 13:36:46 -0700 [thread overview]
Message-ID: <20200621203646.14416-4-bvanassche@acm.org> (raw)
In-Reply-To: <20200621203646.14416-1-bvanassche@acm.org>
This patch makes gcc 10 insert one additional assembly instruction in
io_uring_get_sqe(), namely xor %r8d,%r8d. That shouldn't cause any slowdown
since that instruction does not access memory:
0x0000000000000360 <+0>: mov (%rdi),%rax
0x0000000000000363 <+3>: xor %r8d,%r8d
0x0000000000000366 <+6>: mov (%rax),%ecx
0x0000000000000368 <+8>: mov 0x44(%rdi),%eax
0x000000000000036b <+11>: lea 0x1(%rax),%edx
0x000000000000036e <+14>: mov %edx,%esi
0x0000000000000370 <+16>: sub %ecx,%esi
0x0000000000000372 <+18>: mov 0x18(%rdi),%rcx
0x0000000000000376 <+22>: cmp (%rcx),%esi
0x0000000000000378 <+24>: ja 0x38e <io_uring_get_sqe+46>
0x000000000000037a <+26>: mov 0x10(%rdi),%rcx
0x000000000000037e <+30>: and (%rcx),%eax
0x0000000000000380 <+32>: mov %edx,0x44(%rdi)
0x0000000000000383 <+35>: shl $0x6,%rax
0x0000000000000387 <+39>: add 0x38(%rdi),%rax
0x000000000000038b <+43>: mov %rax,%r8
0x000000000000038e <+46>: mov %r8,%rax
0x0000000000000391 <+49>: retq
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
src/queue.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/src/queue.c b/src/queue.c
index 3db52bd17b86..88e0294c19fb 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -273,16 +273,18 @@ int io_uring_submit_and_wait(struct io_uring *ring, unsigned wait_nr)
return __io_uring_submit_and_wait(ring, wait_nr);
}
-#define __io_uring_get_sqe(sq, __head) ({ \
- unsigned __next = (sq)->sqe_tail + 1; \
- struct io_uring_sqe *__sqe = NULL; \
- \
- if (__next - __head <= *(sq)->kring_entries) { \
- __sqe = &(sq)->sqes[(sq)->sqe_tail & *(sq)->kring_mask];\
- (sq)->sqe_tail = __next; \
- } \
- __sqe; \
-})
+static inline struct io_uring_sqe *
+__io_uring_get_sqe(struct io_uring_sq *sq, unsigned int __head)
+{
+ unsigned int __next = (sq)->sqe_tail + 1;
+ struct io_uring_sqe *__sqe = NULL;
+
+ if (__next - __head <= *(sq)->kring_entries) {
+ __sqe = &(sq)->sqes[(sq)->sqe_tail & *(sq)->kring_mask];
+ (sq)->sqe_tail = __next;
+ }
+ return __sqe;
+}
/*
* Return an sqe to fill. Application must later call io_uring_submit()
next prev parent reply other threads:[~2020-06-21 20:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-21 20:36 [PATCH liburing 0/3] Three small liburing patches Bart Van Assche
2020-06-21 20:36 ` [PATCH liburing 1/3] Makefiles: Enable -Wextra Bart Van Assche
2020-06-21 20:36 ` [PATCH liburing 2/3] src/include/liburing/barrier.h: Use C11 atomics Bart Van Assche
2020-06-21 20:36 ` Bart Van Assche [this message]
2020-06-22 2:50 ` [PATCH liburing 0/3] Three small liburing patches Jens Axboe
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