From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qLN8M-003xit-0x for linux-arm-kernel@lists.infradead.org; Mon, 17 Jul 2023 12:15:42 +0000 Date: Mon, 17 Jul 2023 13:15:18 +0100 Message-ID: <864jm2vind.wl-maz@kernel.org> From: Marc Zyngier Subject: Re: [PATCH] arm64: enable dead code elimination In-Reply-To: <23d94414-b819-eaef-6fac-638bf713d341@huawei.com> References: <20230717080739.1000460-1-wangkefeng.wang@huawei.com> <801e30a093e41c3eebd675f0d224f8d7@kernel.org> <23d94414-b819-eaef-6fac-638bf713d341@huawei.com> MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+lwn-linux-arm-kernel=archive.lwn.net@lists.infradead.org List-Archive: To: Kefeng Wang Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org T24gTW9uLCAxNyBKdWwgMjAyMyAxMjo1NjozOSArMDEwMCwKS2VmZW5nIFdhbmcgPHdhbmdrZWZl bmcud2FuZ0BodWF3ZWkuY29tPiB3cm90ZToKPiAKPiAKPiAKPiBPbiAyMDIzLzcvMTcgMTc6NDIs IE1hcmMgWnluZ2llciB3cm90ZToKPiA+IE9uIDIwMjMtMDctMTcgMDk6MDcsIEtlZmVuZyBXYW5n IHdyb3RlOgo+ID4+IFNlbGVjdCBDT05GSUdfSEFWRV9MRF9ERUFEX0NPREVfREFUQV9FTElNSU5B VElPTiBmb3IgYXJtNjQsIGFsbG93aW5nIHRoZQo+ID4+IHVzZXIgdG8gZW5hYmxlIGRlYWQgY29k ZSBlbGltaW5hdGlvbi4gSW4gb3JkZXIgZm9yIHRoaXMgdG8gd29yaywgZW5zdXJlCj4gPj4gdGhh dCB3ZSBrZWVwIHRoZSBuZWNlc3NhcnkgdGFibGVzIGJ5IGFubm90YXRpbmcgdGhlbSB3aXRoIEtF RVAsIGFsc28gaXQKPiA+PiByZXF1aXJlcyBmdXJ0aGVyIGNoYW5nZXMgdG8gbGlua2VyIHNjcmlw dCB0byBLRUVQIHNvbWUgdGFibGVzIGFuZAo+ID4+IHdpbGRjYXJkCj4gPj4gY29tcGlsZXIgZ2Vu 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17 Jul 2023 13:15:18 +0100 Message-ID: <864jm2vind.wl-maz@kernel.org> From: Marc Zyngier To: Kefeng Wang Cc: Catalin Marinas , Will Deacon , , Subject: Re: [PATCH] arm64: enable dead code elimination In-Reply-To: <23d94414-b819-eaef-6fac-638bf713d341@huawei.com> References: <20230717080739.1000460-1-wangkefeng.wang@huawei.com> <801e30a093e41c3eebd675f0d224f8d7@kernel.org> <23d94414-b819-eaef-6fac-638bf713d341@huawei.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/28.2 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: wangkefeng.wang@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 17 Jul 2023 12:56:39 +0100, Kefeng Wang wrote: >=20 >=20 >=20 > On 2023/7/17 17:42, Marc Zyngier wrote: > > On 2023-07-17 09:07, Kefeng Wang wrote: > >> Select CONFIG_HAVE_LD_DEAD_CODE_DATA_ELIMINATION for arm64, allowing t= he > >> 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. > >>=20 > >> The following comparison is based 6.5-rc2 with defconfig, > >>=20 > >> $ ./scripts/bloat-o-meter vmlinux-base vmlinux-new > >> add/remove: 3/1106 grow/shrink: 4102/6964 up/down: 35704/-99980 (-6427= 6) > >> Function=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 old=C2=A0=C2=A0=C2=A0=C2=A0 new=C2=A0=C2=A0 delta > >> ... > >> Total: Before=3D17888959, After=3D17824683, chg -0.36% > >>=20 > >> add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-44 (-44) > >> Data=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 old=C2=A0=C2=A0=C2=A0=C2=A0 new=C2=A0=C2=A0 delta > >> ... > >> Total: Before=3D4820808, After=3D4820764, chg -0.00% > >>=20 > >> add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-1096 (-1096) > >> RO Data=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 old=C2=A0=C2=A0=C2=A0=C2=A0 new=C2=A0=C2=A0 delta > >> ... > >> Total: Before=3D5179123, After=3D5178027, chg -0.02% > >>=20 > >> $ size vmlinux-base vmlinux > >> =C2=A0=C2=A0 text=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 data=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bss=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 dec= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 hex=C2=A0=C2=A0=C2=A0 filename > >> 25433734=C2=A0 15385766=C2=A0 630656=C2=A0 41450156=C2=A0 2787aac=C2= =A0=C2=A0=C2=A0 vmlinux-base > >> 24756738=C2=A0 15360870=C2=A0 629888=C2=A0 40747496=C2=A0 26dc1e8=C2= =A0=C2=A0=C2=A0 vmlinux-new > >>=20 > >> Memory available after booting, saving 704k on qemu, > >> base: 8084532K/8388608K > >> new:=C2=A0 8085236K/8388608K > >>=20 > >> Signed-off-by: Kefeng Wang > >=20 > > I took this patch for a spin in my tree, and ended up with: > >=20 > > =C2=A0 CC=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 .vmlinux.export.o > > =C2=A0 UPD=C2=A0=C2=A0=C2=A0=C2=A0 include/generated/utsversion.h > > =C2=A0 CC=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 init/version-timestamp.o > > =C2=A0 LD=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 .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 >=20 > I don't find this error with CONFIG_FTRACE_MCOUNT_RECORD or > allyesconfig, does it need special config or gcc version? You tell me! gcc (Debian 10.2.1-6) 10.2.1 20210110 Copyright (C) 2020 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. so hardly something special. This is built with the current state of my NV tree, available here[1] As for the configuration, have a look here[2]. M. [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/l= og/?h=3Dkvm-arm64/nv-6.6-WIP [2] https://paste.debian.net/1286106/ --=20 Without deviation from the norm, progress is not possible.