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Tue, 28 Jun 2022 14:06:23 -0700 (PDT) Date: Tue, 28 Jun 2022 14:04:07 -0700 In-Reply-To: Message-Id: <20220628210407.3343118-1-ndesaulniers@google.com> Mime-Version: 1.0 References: X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=lvO/pmg+aaCb6dPhyGC1GyOCvPueDrrc8Zeso5CaGKE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1656450247; l=9154; s=20211004; h=from:subject; bh=gvpD1o/b8JZSfOr8fCp8TXjM9bVhNEAdI7IvLmzBEEE=; b=nVhj4qFBlP9ZwYTN7PMDRYc5i+NSY2lfu1PyHgoG7UiKXpO4/BxXiJmVb9CLvzUlW9Ck7UIlIhpn CPuZETO6BScAKn5vPYakOUaU35pM/Wk9wOP/6OzF2BDoriqIdGNb X-Mailer: git-send-email 2.37.0.rc0.161.g10f37bed90-goog Subject: [PATCH] kbuild: drop support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 From: Nick Desaulniers To: Masahiro Yamada , Linus Torvalds Cc: arnd@arndb.de, bigeasy@linutronix.de, chris@chrisdown.name, dmitry.torokhov@gmail.com, gustavoars@kernel.org, john.ogness@linutronix.de, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, mikoxyzzz@gmail.com, nathan@kernel.org, ndesaulniers@google.com, oleksandr@redhat.com, quic_eberman@quicinc.com, seanjc@google.com, tglx@linutronix.de, vbabka@suse.cz, x86@kernel.org, linux-snps-arc@lists.infradead.org, Vineet Gupta X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220628_140626_140951_ADBFAAA9 X-CRM114-Status: GOOD ( 14.33 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: Spam detection software, running on the system "bombadil.infradead.org", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: The difference in most compilers between `-O3` and `-O2` is mostly down to whether loops with statically determinable trip counts are fully unrolled vs unrolled to a multiple of SIMD width. This patch is effectively a revert of commit 15f5db60a137 ("kbuild,arc: add CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 for ARC") without re-adding ARCH_CFLAGS Content analysis details: (-7.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:114a listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.0 DKIMWL_WL_MED DKIMwl.org - Medium trust sender X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org The difference in most compilers between `-O3` and `-O2` is mostly down to whether loops with statically determinable trip counts are fully unrolled vs unrolled to a multiple of SIMD width. This patch is effectively a revert of commit 15f5db60a137 ("kbuild,arc: add CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 for ARC") without re-adding ARCH_CFLAGS Ever since commit cfdbc2e16e65 ("ARC: Build system: Makefiles, Kconfig, Linker script") ARC has been built with -O3, though the reason for doing so was not specified in inline comments or the commit message. This commit does not re-add -O3 to arch/arc/Makefile. Folks looking to experiment with `-O3` (or any compiler flag for that matter) may pass them along to the command line invocation of make: $ make KCFLAGS=-O3 Code that looks to re-add an explicit Kconfig option for `-O3` should provide: 1. A rigorous and reproducible performance profile of a reasonable userspace workload that demonstrates a hot loop in the kernel that would benefit from `-O3` over `-O2`. 2. Disassembly of said loop body before and after. 3. Provides stats on terms of increase in file size. Link: https://lore.kernel.org/linux-kbuild/CA+55aFz2sNBbZyg-_i8_Ldr2e8o9dfvdSfHHuRzVtP2VMAUWPg@mail.gmail.com/ Signed-off-by: Nick Desaulniers --- Makefile | 2 -- arch/arc/configs/axs101_defconfig | 1 - arch/arc/configs/axs103_defconfig | 1 - arch/arc/configs/axs103_smp_defconfig | 1 - arch/arc/configs/haps_hs_defconfig | 1 - arch/arc/configs/haps_hs_smp_defconfig | 1 - arch/arc/configs/hsdk_defconfig | 1 - arch/arc/configs/nsim_700_defconfig | 1 - arch/arc/configs/nsimosci_defconfig | 1 - arch/arc/configs/nsimosci_hs_defconfig | 1 - arch/arc/configs/nsimosci_hs_smp_defconfig | 1 - arch/arc/configs/tb10x_defconfig | 1 - arch/arc/configs/vdk_hs38_defconfig | 1 - arch/arc/configs/vdk_hs38_smp_defconfig | 1 - init/Kconfig | 7 ------- 15 files changed, 22 deletions(-) diff --git a/Makefile b/Makefile index 8973b285ce6c..b69f6cd7f2e2 100644 --- a/Makefile +++ b/Makefile @@ -755,8 +755,6 @@ KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE KBUILD_CFLAGS += -O2 -else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 -KBUILD_CFLAGS += -O3 else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE KBUILD_CFLAGS += -Os endif diff --git a/arch/arc/configs/axs101_defconfig b/arch/arc/configs/axs101_defconfig index 0016149f9583..e31a8ebc3ecc 100644 --- a/arch/arc/configs/axs101_defconfig +++ b/arch/arc/configs/axs101_defconfig @@ -9,7 +9,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y # CONFIG_VM_EVENT_COUNTERS is not set diff --git a/arch/arc/configs/axs103_defconfig b/arch/arc/configs/axs103_defconfig index 5b031582a1cf..e0e8567f0d75 100644 --- a/arch/arc/configs/axs103_defconfig +++ b/arch/arc/configs/axs103_defconfig @@ -9,7 +9,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y # CONFIG_VM_EVENT_COUNTERS is not set diff --git a/arch/arc/configs/axs103_smp_defconfig b/arch/arc/configs/axs103_smp_defconfig index d4eec39e0112..fcbc952bc75b 100644 --- a/arch/arc/configs/axs103_smp_defconfig +++ b/arch/arc/configs/axs103_smp_defconfig @@ -9,7 +9,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y # CONFIG_VM_EVENT_COUNTERS is not set diff --git a/arch/arc/configs/haps_hs_defconfig b/arch/arc/configs/haps_hs_defconfig index 7337cdf4ffdd..d87ad7e88d62 100644 --- a/arch/arc/configs/haps_hs_defconfig +++ b/arch/arc/configs/haps_hs_defconfig @@ -11,7 +11,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EXPERT=y CONFIG_PERF_EVENTS=y # CONFIG_COMPAT_BRK is not set diff --git a/arch/arc/configs/haps_hs_smp_defconfig b/arch/arc/configs/haps_hs_smp_defconfig index bc927221afc0..8d82cdb7f86a 100644 --- a/arch/arc/configs/haps_hs_smp_defconfig +++ b/arch/arc/configs/haps_hs_smp_defconfig @@ -11,7 +11,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y # CONFIG_VM_EVENT_COUNTERS is not set diff --git a/arch/arc/configs/hsdk_defconfig b/arch/arc/configs/hsdk_defconfig index aa000075a575..f856b03e0fb5 100644 --- a/arch/arc/configs/hsdk_defconfig +++ b/arch/arc/configs/hsdk_defconfig @@ -9,7 +9,6 @@ CONFIG_NAMESPACES=y # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y CONFIG_BLK_DEV_RAM=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y # CONFIG_VM_EVENT_COUNTERS is not set diff --git a/arch/arc/configs/nsim_700_defconfig b/arch/arc/configs/nsim_700_defconfig index 326f6cde7826..a1ce12bf5b16 100644 --- a/arch/arc/configs/nsim_700_defconfig +++ b/arch/arc/configs/nsim_700_defconfig @@ -11,7 +11,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_KALLSYMS_ALL=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y diff --git a/arch/arc/configs/nsimosci_defconfig b/arch/arc/configs/nsimosci_defconfig index bf39a0091679..ca10f4a2c823 100644 --- a/arch/arc/configs/nsimosci_defconfig +++ b/arch/arc/configs/nsimosci_defconfig @@ -10,7 +10,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_KALLSYMS_ALL=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y diff --git a/arch/arc/configs/nsimosci_hs_defconfig b/arch/arc/configs/nsimosci_hs_defconfig index 7121bd71c543..31b6ec3683c6 100644 --- a/arch/arc/configs/nsimosci_hs_defconfig +++ b/arch/arc/configs/nsimosci_hs_defconfig @@ -10,7 +10,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_KALLSYMS_ALL=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y diff --git a/arch/arc/configs/nsimosci_hs_smp_defconfig b/arch/arc/configs/nsimosci_hs_smp_defconfig index f9863b294a70..41a0037f48a5 100644 --- a/arch/arc/configs/nsimosci_hs_smp_defconfig +++ b/arch/arc/configs/nsimosci_hs_smp_defconfig @@ -8,7 +8,6 @@ CONFIG_IKCONFIG_PROC=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_PERF_EVENTS=y # CONFIG_COMPAT_BRK is not set CONFIG_KPROBES=y diff --git a/arch/arc/configs/tb10x_defconfig b/arch/arc/configs/tb10x_defconfig index a12656ec0072..d93b65008d4a 100644 --- a/arch/arc/configs/tb10x_defconfig +++ b/arch/arc/configs/tb10x_defconfig @@ -14,7 +14,6 @@ CONFIG_INITRAMFS_SOURCE="../tb10x-rootfs.cpio" CONFIG_INITRAMFS_ROOT_UID=2100 CONFIG_INITRAMFS_ROOT_GID=501 # CONFIG_RD_GZIP is not set -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_KALLSYMS_ALL=y # CONFIG_AIO is not set CONFIG_EMBEDDED=y diff --git a/arch/arc/configs/vdk_hs38_defconfig b/arch/arc/configs/vdk_hs38_defconfig index d7c858df520c..0c3b21416819 100644 --- a/arch/arc/configs/vdk_hs38_defconfig +++ b/arch/arc/configs/vdk_hs38_defconfig @@ -4,7 +4,6 @@ CONFIG_HIGH_RES_TIMERS=y CONFIG_IKCONFIG=y CONFIG_IKCONFIG_PROC=y CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y # CONFIG_VM_EVENT_COUNTERS is not set diff --git a/arch/arc/configs/vdk_hs38_smp_defconfig b/arch/arc/configs/vdk_hs38_smp_defconfig index 015c1d43889e..f9ad9d3ee702 100644 --- a/arch/arc/configs/vdk_hs38_smp_defconfig +++ b/arch/arc/configs/vdk_hs38_smp_defconfig @@ -4,7 +4,6 @@ CONFIG_HIGH_RES_TIMERS=y CONFIG_IKCONFIG=y CONFIG_IKCONFIG_PROC=y CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y # CONFIG_VM_EVENT_COUNTERS is not set diff --git a/init/Kconfig b/init/Kconfig index c7900e8975f1..1b4d8acc3def 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1401,13 +1401,6 @@ config CC_OPTIMIZE_FOR_PERFORMANCE with the "-O2" compiler flag for best performance and most helpful compile-time warnings. -config CC_OPTIMIZE_FOR_PERFORMANCE_O3 - bool "Optimize more for performance (-O3)" - depends on ARC - help - Choosing this option will pass "-O3" to your compiler to optimize - the kernel yet more for performance. - config CC_OPTIMIZE_FOR_SIZE bool "Optimize for size (-Os)" help