From: Marc Zyngier <maz@kernel.org>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: enable dead code elimination
Date: Mon, 17 Jul 2023 10:42:15 +0100 [thread overview]
Message-ID: <801e30a093e41c3eebd675f0d224f8d7@kernel.org> (raw)
In-Reply-To: <20230717080739.1000460-1-wangkefeng.wang@huawei.com>
On 2023-07-17 09:07, Kefeng Wang wrote:
> Select CONFIG_HAVE_LD_DEAD_CODE_DATA_ELIMINATION for arm64, allowing
> the
> user to enable dead code elimination. In order for this to work, ensure
> that 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.
>
> The following comparison is based 6.5-rc2 with defconfig,
>
> $ ./scripts/bloat-o-meter vmlinux-base vmlinux-new
> add/remove: 3/1106 grow/shrink: 4102/6964 up/down: 35704/-99980
> (-64276)
> Function old new delta
> ...
> Total: Before=17888959, After=17824683, chg -0.36%
>
> add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-44 (-44)
> Data old new delta
> ...
> Total: Before=4820808, After=4820764, chg -0.00%
>
> add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-1096 (-1096)
> RO Data old new delta
> ...
> Total: Before=5179123, After=5178027, chg -0.02%
>
> $ size vmlinux-base vmlinux
> text data bss dec hex filename
> 25433734 15385766 630656 41450156 2787aac vmlinux-base
> 24756738 15360870 629888 40747496 26dc1e8 vmlinux-new
>
> Memory available after booting, saving 704k on qemu,
> base: 8084532K/8388608K
> new: 8085236K/8388608K
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
I took this patch for a spin in my tree, and ended up with:
CC .vmlinux.export.o
UPD include/generated/utsversion.h
CC init/version-timestamp.o
LD .tmp_vmlinux.kallsyms1
ld: init/main.o(__patchable_function_entries): error: need linked-to
section for --gc-sections
make[2]: *** [scripts/Makefile.vmlinux:36: vmlinux] Error 1
make[1]: *** [/home/maz/hot-poop/arm-platforms/Makefile:1238: vmlinux]
Error 2
make: *** [Makefile:234: __sub-make] Error 2
so it's probably not ready for prime time.
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2023-07-17 9:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-17 8:07 [PATCH] arm64: enable dead code elimination Kefeng Wang
2023-07-17 9:24 ` Will Deacon
2023-07-17 11:20 ` Kefeng Wang
2024-01-25 13:45 ` Yuntao Liu
2023-07-17 9:42 ` Marc Zyngier [this message]
2023-07-17 11:56 ` Kefeng Wang
2023-07-17 12:15 ` Marc Zyngier
2023-07-18 11:11 ` Kefeng Wang
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