From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Guo Ren <guoren@kernel.org>, Waiman Long <llong@redhat.com>,
Huacai Chen <chenhuacai@gmail.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Huacai Chen <chenhuacai@loongson.cn>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Linux-Arch <linux-arch@vger.kernel.org>,
Rui Wang <wangrui@loongson.cn>,
Xuefeng Li <lixuefeng@loongson.cn>,
Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH RFC 1/2] arch: Introduce ARCH_HAS_HW_XCHG_SMALL
Date: Tue, 27 Jul 2021 13:05:05 +0200 [thread overview]
Message-ID: <YP/oYc1A39bMS87H@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YP9vp8/acj9TpwyZ@boqun-archlinux>
On Tue, Jul 27, 2021 at 10:29:59AM +0800, Boqun Feng wrote:
> > "How to implement xchg_tail" shouldn't force with _Q_PENDING_BITS, but
> > the arch could choose.
>
> I actually agree with this part, but this patchset failed to provide
> enough evidences on why we should choose xchg_tail() implementation
> based on whether hardware has xchg16, more precisely, for an archtecture
> which doesn't have a hardware xchg16, why cmpxchg emulated xchg16() is
> worse than a "load+cmpxchg) implemeneted xchg_tail()? If it's a
> performance reason, please show some numbers.
Right. Their problem is their broken xchg16() implementation.
next prev parent reply other threads:[~2021-07-27 11:08 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-24 12:36 [PATCH RFC 1/2] arch: Introduce ARCH_HAS_HW_XCHG_SMALL Huacai Chen
2021-07-24 12:36 ` [PATCH RFC 2/2] qspinlock: Use ARCH_HAS_HW_XCHG_SMALL to select _Q_PENDING_BITS definition Huacai Chen
2021-07-24 19:24 ` [PATCH RFC 1/2] arch: Introduce ARCH_HAS_HW_XCHG_SMALL Arnd Bergmann
2021-07-25 3:06 ` Jiaxun Yang
2021-07-25 10:08 ` Arnd Bergmann
2021-07-26 8:36 ` Geert Uytterhoeven
2021-07-26 8:56 ` Huacai Chen
2021-07-26 10:39 ` Boqun Feng
2021-07-26 16:41 ` Guo Ren
2021-07-26 17:03 ` Boqun Feng
2021-07-26 21:20 ` Waiman Long
2021-07-27 1:27 ` Guo Ren
2021-07-27 2:29 ` Boqun Feng
2021-07-27 2:46 ` Waiman Long
2021-07-27 11:05 ` Peter Zijlstra [this message]
2021-07-28 10:40 ` Huacai Chen
2021-07-28 11:01 ` Peter Zijlstra
2021-07-29 16:38 ` Huacai Chen
2021-07-27 10:17 ` Peter Zijlstra
2021-07-27 1:07 ` Guo Ren
2021-07-27 1:52 ` Wang Rui
2021-07-27 11:03 ` Peter Zijlstra
2021-07-27 2:00 ` Boqun Feng
2021-07-27 10:50 ` Peter Zijlstra
2021-07-27 10:12 ` Peter Zijlstra
2021-07-26 9:00 ` Arnd Bergmann
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