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Date: Mon, 3 Jun 2024 20:55:09 +0800
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Subject: Re: [PATCH-next v4] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
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To: Russell King <linux@armlinux.org.uk>, Ard Biesheuvel <ardb@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Fangrui Song <maskray@google.com>, Linus
 Walleij <linus.walleij@linaro.org>, <geert@linux-m68k.org>,
	<linux@armlinux.org.uk>, <afd@ti.com>, <akpm@linux-foundation.org>,
	<kirill.shutemov@linux.intel.com>, <geert+renesas@glider.be>,
	<corbet@lwn.net>, <rppt@kernel.org>, <robh@kernel.org>, <tglx@linutronix.de>,
	<linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>
CC: <liuyuntao12@huawei.com>
References: <20240316023932.700685-1-liuyuntao12@huawei.com>
 <CAMj1kXH5bpbagOO+WFwxp4=U=Kbu9RVbPrEemt80S7My1jTEdw@mail.gmail.com>
From: "liuyuntao (F)" <liuyuntao12@huawei.com>
In-Reply-To: <CAMj1kXH5bpbagOO+WFwxp4=U=Kbu9RVbPrEemt80S7My1jTEdw@mail.gmail.com>
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Gentle ping

On 2024/3/20 1:12, Ard Biesheuvel wrote:
> On Sat, 16 Mar 2024 at 03:44, Yuntao Liu <liuyuntao12@huawei.com> wrote:
>>
>> The current arm32 architecture does not yet support the
>> HAVE_LD_DEAD_CODE_DATA_ELIMINATION feature. arm32 is widely used in
>> embedded scenarios, and enabling this feature would be beneficial for
>> reducing the size of the kernel image.
>>
>> In order to make this work, we keep the necessary tables by annotating
>> them with KEEP, also it requires further changes to linker script to KEEP
>> some tables and wildcard compiler generated sections into the right place.
>> When using ld.lld for linking, KEEP is not recognized within the OVERLAY
>> command, and Ard proposed a concise method to solve this problem.
>>
>> It boots normally with defconfig, vexpress_defconfig and tinyconfig.
>>
>> The size comparison of zImage is as follows:
>> defconfig       vexpress_defconfig      tinyconfig
>> 5137712         5138024                 424192          no dce
>> 5032560         4997824                 298384          dce
>> 2.0%            2.7%                    29.7%           shrink
>>
>> When using smaller config file, there is a significant reduction in the
>> size of the zImage.
>>
>> We also tested this patch on a commercially available single-board
>> computer, and the comparison is as follows:
>> a15eb_config
>> 2161384         no dce
>> 2092240         dce
>> 3.2%            shrink
>>
>> The zImage size has been reduced by approximately 3.2%, which is 70KB on
>> 2.1M.
>>
>> Signed-off-by: Yuntao Liu <liuyuntao12@huawei.com>
>> Tested-by: Arnd Bergmann <arnd@arndb.de>
>> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> 
> Reviewed-by: Ard Biesheuvel <ardb@kernel.org>