linux-kernel - Re: [PATCH v5 08/14] arm64: Import latest optimization of memcpy

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Date:   Tue, 1 Jun 2021 15:33:58 +0530
From:   Sunil Kovvuri <sunil.kovvuri@...il.com>
To:     Oliver Swede <oli.swede@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>, will@...nel.org,
        Robin Murphy <robin.murphy@....com>,
        linux-arm-kernel@...ts.indradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Sunil Goutham <sgoutham@...vell.com>,
        George Cherian <gcherian@...vell.com>
Subject: Re: [PATCH v5 08/14] arm64: Import latest optimization of memcpy

On Mon, Sep 14, 2020 at 8:44 PM Oliver Swede <oli.swede@....com> wrote:
>
> From: Sam Tebbs <sam.tebbs@....com>
>
> Import the latest memcpy implementation into memcpy,
> copy_{from, to and in}_user.
> The implementation of the user routines is separated into two forms:
> one for when UAO is enabled and one for when UAO is disabled, with
> the two being chosen between with a runtime patch.
> This avoids executing the many NOPs emitted when UAO is disabled.
>
> The project containing optimized implementations for various library
> functions has now been renamed from 'cortex-strings' to
> 'optimized-routines', and the new upstream source is
> string/aarch64/memcpy.S as of commit 4c175c8be12 in
> https://github.com/ARM-software/optimized-routines.
>
> Signed-off-by: Sam Tebbs <sam.tebbs@....com>
> [ rm: add UAO fixups, streamline copy_exit paths, expand commit message ]
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> [ os: import newer memcpy algorithm, update commit message ]
> Signed-off-by: Oliver Swede <oli.swede@....com>
> ---
>  arch/arm64/include/asm/alternative.h |  36 ---
>  arch/arm64/lib/copy_from_user.S      | 113 ++++++--
>  arch/arm64/lib/copy_in_user.S        | 129 +++++++--
>  arch/arm64/lib/copy_template.S       | 375 +++++++++++++++------------
>  arch/arm64/lib/copy_template_user.S  |  24 ++
>  arch/arm64/lib/copy_to_user.S        | 112 ++++++--
>  arch/arm64/lib/copy_user_fixup.S     |  14 +
>  arch/arm64/lib/memcpy.S              |  47 ++--
>  8 files changed, 557 insertions(+), 293 deletions(-)
>  create mode 100644 arch/arm64/lib/copy_template_user.S
>  create mode 100644 arch/arm64/lib/copy_user_fixup.S

Do you have any performance data with this patch ?
I see these patches are still not pushed to mainline, any reasons ?

Also curious to know why 128bit registers are not considered, similar to
https://android.googlesource.com/platform/bionic.git/+/a71b4c3f144a516826e8ac5b262099b920c49ce0/libc/arch-arm64/generic-neon/bionic/memcpy.S

Thanks,
Sunil.