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Date:   Wed, 5 Apr 2023 09:37:04 -0700
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Subject: Re: [PATCH v2 0/5] locking: Introduce local{,64}_try_cmpxchg
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To:     Uros Bizjak <ubizjak@gmail.com>, linux-alpha@vger.kernel.org,
        loongarch@lists.linux.dev, linux-mips@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
        linux-arch@vger.kernel.org, linux-perf-users@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     Richard Henderson <richard.henderson@linaro.org>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Arnd Bergmann <arnd@arndb.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>, Will Deacon <will@kernel.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Jun Yi <yijun@loongson.cn>
References: <20230405141710.3551-1-ubizjak@gmail.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20230405141710.3551-1-ubizjak@gmail.com>
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On 4/5/23 07:17, Uros Bizjak wrote:
> Add generic and target specific support for local{,64}_try_cmpxchg
> and wire up support for all targets that use local_t infrastructure.

I feel like I'm missing some context.

What are the actual end user visible effects of this series?  Is there a
measurable decrease in perf overhead?  Why go to all this trouble for
perf?  Who else will use local_try_cmpxchg()?

I'm all for improving things, and perf is an important user.  But, if
the goal here is improving performance, it would be nice to see at least
a stab at quantifying the performance delta.