From: Will Deacon <will@kernel.org>
To: Yury Norov <yury.norov@gmail.com>
Cc: linux-arch@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: enable GENERIC_FIND_FIRST_BIT
Date: Mon, 7 Dec 2020 11:25:30 +0000 [thread overview]
Message-ID: <20201207112530.GB4379@willie-the-truck> (raw)
In-Reply-To: <20201205165406.108990-1-yury.norov@gmail.com>
On Sat, Dec 05, 2020 at 08:54:06AM -0800, Yury Norov wrote:
> ARM64 doesn't implement find_first_{zero}_bit in arch code and doesn't
> enable it in config. It leads to using find_next_bit() which is less
> efficient:
[...]
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1515f6f153a0..2b90ef1f548e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -106,6 +106,7 @@ config ARM64
> select GENERIC_CPU_AUTOPROBE
> select GENERIC_CPU_VULNERABILITIES
> select GENERIC_EARLY_IOREMAP
> + select GENERIC_FIND_FIRST_BIT
Does this actually make any measurable difference? The disassembly with
or without this is _very_ similar for me (clang 11).
Will
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next prev parent reply other threads:[~2020-12-07 11:26 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-05 16:54 [PATCH] arm64: enable GENERIC_FIND_FIRST_BIT Yury Norov
2020-12-07 11:25 ` Will Deacon [this message]
2020-12-08 1:59 ` Yury Norov
2020-12-08 10:35 ` Will Deacon
2021-02-24 5:27 ` Yury Norov
2021-02-24 9:33 ` Will Deacon
2021-02-24 11:52 ` Alexander Lobakin
2021-02-24 15:44 ` Yury Norov
2021-02-25 11:53 ` Alexander Lobakin
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