From: Catalin Marinas <catalin.marinas@arm.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: will@kernel.org, linux-arm-kernel@lists.infradead.org,
yangyingliang@huawei.com, shenkai8@huawei.com
Subject: Re: [PATCH 7/8] arm64: Better optimised memchr()
Date: Fri, 14 May 2021 15:55:13 +0100 [thread overview]
Message-ID: <20210514145513.GB28888@arm.com> (raw)
In-Reply-To: <68d3229c208780fdde88ba48e14fcde8c50f6e76.1620738177.git.robin.murphy@arm.com>
On Tue, May 11, 2021 at 05:12:37PM +0100, Robin Murphy wrote:
> Although we implement our own assembly version of memchr(), it turns
> out to be barely any better than what GCC can generate for the generic
> C version (and would go wrong if the size_t argument were ever large
> enough to be interpreted as negative). Unfortunately we can't import the
> tuned implementation from the Arm optimized-routines library, since that
> has some Advanced SIMD parts which are not really viable for general
> kernel library code. What we can do, however, is pep things up with some
> relatively straightforward word-at-a-time logic for larger calls.
>
> Adding some timing to optimized-routines' memchr() test for a simple
> benchmark, overall this version comes in around half as fast as the SIMD
> code, but still nearly 4x faster than our existing implementation.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
I haven't reviewed the code yet but wondering - could we write this in C
using load_unaligned_zeropad()?
--
Catalin
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next prev parent reply other threads:[~2021-05-14 14:56 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 16:12 [PATCH 0/8] arm64: String function updates Robin Murphy
2021-05-11 16:12 ` [PATCH 1/8] arm64: Import latest version of Cortex Strings' memcmp Robin Murphy
2021-05-12 13:28 ` Mark Rutland
2021-05-12 13:38 ` Robin Murphy
2021-05-12 14:51 ` Szabolcs Nagy
2021-05-26 10:17 ` Mark Rutland
2021-05-11 16:12 ` [PATCH 2/8] arm64: Import latest version of Cortex Strings' strcmp Robin Murphy
2021-05-11 16:12 ` [PATCH 3/8] arm64: Import updated version of Cortex Strings' strlen Robin Murphy
2021-05-11 16:12 ` [PATCH 4/8] arm64: Import latest version of Cortex Strings' strncmp Robin Murphy
2021-05-11 16:12 ` [PATCH 5/8] arm64: Add assembly annotations for weak-PI-alias madness Robin Murphy
2021-05-11 16:12 ` [PATCH 6/8] arm64: Import latest memcpy()/memmove() implementation Robin Murphy
2021-05-11 16:12 ` [PATCH 7/8] arm64: Better optimised memchr() Robin Murphy
2021-05-14 14:55 ` Catalin Marinas [this message]
2021-05-14 18:38 ` Robin Murphy
2021-05-11 16:12 ` [PATCH 8/8] arm64: Rewrite __arch_clear_user() Robin Murphy
2021-05-12 10:48 ` Mark Rutland
2021-05-12 11:31 ` Robin Murphy
2021-05-12 13:06 ` Mark Rutland
2021-05-12 13:51 ` Robin Murphy
2021-05-14 11:57 ` [PATCH v2] " Robin Murphy
2021-05-26 11:15 ` Mark Rutland
2021-05-27 13:24 ` Robin Murphy
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