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a0727c7383
While looking at io_fill_cqe_req()'s asm I stumbled on our trace points
turning into the chunk below:
trace_io_uring_complete(req->ctx, req, req->cqe.user_data,
req->cqe.res, req->cqe.flags,
req->extra1, req->extra2);
io_uring/io_uring.c:898: trace_io_uring_complete(req->ctx, req, req->cqe.user_data,
movq 232(%rbx), %rdi # req_44(D)->big_cqe.extra2, _5
movq 224(%rbx), %rdx # req_44(D)->big_cqe.extra1, _6
movl 84(%rbx), %r9d # req_44(D)->cqe.D.81184.flags, _7
movl 80(%rbx), %r8d # req_44(D)->cqe.res, _8
movq 72(%rbx), %rcx # req_44(D)->cqe.user_data, _9
movq 88(%rbx), %rsi # req_44(D)->ctx, _10
./arch/x86/include/asm/jump_label.h:27: asm_volatile_goto("1:"
1:jmp .L1772 # objtool NOPs this #
...
It does a jump_label for actual tracing, but those 6 moves will stay
there in the hottest io_uring path. As an optimisation, add a
trace_io_uring_complete_enabled() check, which is also uses jump_labels,
it tricks the compiler into behaving. It removes the junk without
changing anything else int the hot path.
Note: apparently, it's not only me noticing it, and people are also
working it around. We should remove the check when it's solved
generically or rework tracing.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/555d8312644b3776f4be7e23f9b92943875c4bc7.1692916914.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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| .. | ||
| advise.c | ||
| advise.h | ||
| alloc_cache.h | ||
| cancel.c | ||
| cancel.h | ||
| epoll.c | ||
| epoll.h | ||
| fdinfo.c | ||
| fdinfo.h | ||
| filetable.c | ||
| filetable.h | ||
| fs.c | ||
| fs.h | ||
| io-wq.c | ||
| io-wq.h | ||
| io_uring.c | ||
| io_uring.h | ||
| kbuf.c | ||
| kbuf.h | ||
| Makefile | ||
| msg_ring.c | ||
| msg_ring.h | ||
| net.c | ||
| net.h | ||
| nop.c | ||
| nop.h | ||
| notif.c | ||
| notif.h | ||
| opdef.c | ||
| opdef.h | ||
| openclose.c | ||
| openclose.h | ||
| poll.c | ||
| poll.h | ||
| refs.h | ||
| rsrc.c | ||
| rsrc.h | ||
| rw.c | ||
| rw.h | ||
| slist.h | ||
| splice.c | ||
| splice.h | ||
| sqpoll.c | ||
| sqpoll.h | ||
| statx.c | ||
| statx.h | ||
| sync.c | ||
| sync.h | ||
| tctx.c | ||
| tctx.h | ||
| timeout.c | ||
| timeout.h | ||
| uring_cmd.c | ||
| uring_cmd.h | ||
| xattr.c | ||
| xattr.h | ||