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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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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
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...

  parent reply	other threads:[~2023-07-17  9:42 UTC|newest]

Thread overview: 16+ 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  8:07 ` Kefeng Wang
2023-07-17  9:24 ` Will Deacon
2023-07-17  9:24   ` Will Deacon
2023-07-17 11:20   ` Kefeng Wang
2023-07-17 11:20     ` Kefeng Wang
2024-01-25 13:45   ` Yuntao Liu
2024-01-25 13:45     ` Yuntao Liu
2023-07-17  9:42 ` Marc Zyngier [this message]
2023-07-17  9:42   ` Marc Zyngier
2023-07-17 11:56   ` Kefeng Wang
2023-07-17 11:56     ` Kefeng Wang
2023-07-17 12:15     ` Marc Zyngier
2023-07-17 12:15       ` Marc Zyngier
2023-07-18 11:11       ` Kefeng Wang
2023-07-18 11:11         ` Kefeng Wang

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