From: Peter Zijlstra <peterz@infradead.org>
To: will@kernel.org, boqun.feng@gmail.com
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
mark.rutland@arm.com, elver@google.com, keescook@chromium.org,
hch@infradead.org, torvalds@linux-foundation.org,
axboe@kernel.dk
Subject: Re: [RFC][PATCH 3/5] refcount: Improve out-of-line code-gen
Date: Thu, 9 Dec 2021 09:33:05 +0100 [thread overview]
Message-ID: <20211209083305.GN16608@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20211208183906.548393311@infradead.org>
On Wed, Dec 08, 2021 at 07:36:58PM +0100, Peter Zijlstra wrote:
> Allow a number of ops to tail-call refcount_warn_saturate() in order
> to generate smaller out-of-line code.
>
> text data bss dec hex filename
> 97341 4985 1116 103442 19412 defconfig-build/kernel/events/core.o
> 97299 4985 1116 103400 193e8 defconfig-build/kernel/events/core.o
>
This patch also makes GCC do worse code-gen on the fast path, so I'll
drop it.
For some obscure raisin it causes this:
ring_buffer_put:
a950: f0 ff 0f lock decl (%rdi)
a953: 7c 20 jl a975 <ring_buffer_put+0x25>
a955: 74 01 je a958 <ring_buffer_put+0x8>
a957: c3 ret
ring_buffer_put:
a940: 53 push %rbx
a941: 48 89 fb mov %rdi,%rbx
a944: f0 ff 0f lock decl (%rdi)
a947: 7c 04 jl a94d <ring_buffer_put+0xd>
a949: 74 10 je a95b <ring_buffer_put+0x1b>
a94b: 5b pop %rbx
a94c: c3 ret
Which is just unacceptible...
next prev parent reply other threads:[~2021-12-09 8:33 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-08 18:36 [RFC][PATCH 0/5] refcount: Improve code-gen Peter Zijlstra
2021-12-08 18:36 ` [RFC][PATCH 1/5] atomic: Introduce atomic_{inc,dec,dec_and_test}_ofl() Peter Zijlstra
2021-12-09 12:42 ` Mark Rutland
2021-12-09 13:34 ` Peter Zijlstra
2021-12-08 18:36 ` [RFC][PATCH 2/5] refcount: Use atomic_*_ofl() Peter Zijlstra
2021-12-08 19:19 ` Peter Zijlstra
2021-12-08 20:56 ` Peter Zijlstra
2021-12-09 13:17 ` Mark Rutland
2021-12-09 17:00 ` Mark Rutland
2021-12-08 18:36 ` [RFC][PATCH 3/5] refcount: Improve out-of-line code-gen Peter Zijlstra
2021-12-09 8:33 ` Peter Zijlstra [this message]
2021-12-09 17:51 ` Linus Torvalds
2021-12-08 18:36 ` [RFC][PATCH 4/5] atomic,x86: Implement atomic_dec_and_test_ofl() Peter Zijlstra
2021-12-08 18:37 ` [RFC][PATCH 5/5] atomic: Document the atomic_{}_ofl() functions Peter Zijlstra
2021-12-09 8:25 ` [RFC][PATCH 0/5] refcount: Improve code-gen Peter Zijlstra
2021-12-09 16:19 ` Jens Axboe
2021-12-09 16:51 ` Peter Zijlstra
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