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Sun, 30 Nov 2025 04:43:35 -0800 (PST) From: Xie Yuanbin To: acme@kernel.org, adrian.hunter@intel.com, agordeev@linux.ibm.com, akpm@linux-foundation.org, alex@ghiti.fr, alexander.shishkin@linux.intel.com, andreas@gaisler.com, anna-maria@linutronix.de, anshuman.khandual@arm.com, aou@eecs.berkeley.edu, arnd@arndb.de, borntraeger@linux.ibm.com, bp@alien8.de, bsegall@google.com, dave.hansen@linux.intel.com, davem@davemloft.net, david@kernel.org, dietmar.eggemann@arm.com, frederic@kernel.org, gor@linux.ibm.com, hca@linux.ibm.com, hpa@zytor.com, irogers@google.com, james.clark@linaro.org, jolsa@kernel.org, juri.lelli@redhat.com, justinstitt@google.com, lorenzo.stoakes@oracle.com, luto@kernel.org, mark.rutland@arm.com, mathieu.desnoyers@efficios.com, max.kellermann@ionos.com, mgorman@suse.de, mingo@redhat.com, morbo@google.com, namhyung@kernel.org, nathan@kernel.org, nick.desaulniers+lkml@gmail.com, nysal@linux.ibm.com, palmer@dabbelt.com, paulmck@kernel.org, peterz@infradead.org, pjw@kernel.org, riel@surriel.com, rostedt@goodmis.org, ryan.roberts@arm.com, segher@kernel.crashing.org, svens@linux.ibm.com, tglx@linutronix.de, thuth@redhat.com, urezki@gmail.com, vincent.guittot@linaro.org, vschneid@redhat.com, linux@armlinux.org.uk Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-perf-users@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH v4 0/3] Optimize code generation during context switching Date: Sun, 30 Nov 2025 20:43:04 +0800 Message-ID: <20251130124304.184107-1-qq570070308@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251123121827.1304-1-qq570070308@gmail.com> References: <20251123121827.1304-1-qq570070308@gmail.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sun, 23 Nov 2025 20:18:24 +0800, Xie Yuanbin wrote: > This series of patches primarily make some functions called in context > switching as always inline to optimize performance. Here is the > performance test data for these patches: > Time spent on calling finish_task_switch(), the unit is tsc from x86: > | test scenario | old | new | delta | > | gcc 15.2 | 13.94 | 12.40 | 1.54 (-11.1%) | > | gcc 15.2 + spectre_v2 | 24.78 | 13.70 | 11.08 (-44.7%) | > | clang 21.1.4 | 13.90 | 12.71 | 1.19 (- 8.6%) | > | clang 21.1.4 + spectre_v2 | 29.01 | 18.91 | 10.1 (-34.8%) | Hi everyone, I also conducted a performance test on raspberry pi 3b. I hope this will be helpful in merging the patch. The following is the test data: Time spent on calling finish_task_switch(), the clocksource and unit is cntvct_el0 from aarch64: | test scenario | old | new | delta | | gcc 15.2 | 2.00 | 1.68 | 0.32 (-16.0%) | | clang 21.1.6 | 2.15 | 1.68 | 0.47 (-23.5%) | Since raspberry pi 3b use a cortex-a53 processor, it is not affected by the spectre v2 vulnerability, as is defined in arch/arm64/kernel/proton-pack.c: ```c static const struct midr_range spectre_v2_safe_list[] = { MIDR_ALL_VERSIONS(MIDR_CORTEX_A35), MIDR_ALL_VERSIONS(MIDR_CORTEX_A53), MIDR_ALL_VERSIONS(MIDR_CORTEX_A55), MIDR_ALL_VERSIONS(MIDR_BRAHMA_B53), MIDR_ALL_VERSIONS(MIDR_HISI_TSV110), MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_2XX_SILVER), MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_SILVER), MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_SILVER), { /* sentinel */ } }; ``` Link: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm64/kernel/proton-pack.c?id=7d31f578f3230f3b7b33b0930b08f9afd8429817#n152 Perhaps I can test the performace with spectre_v2 mitigation enabled on a raspberry pi 4b in the future. In order to make the test result stable, I fixed the cpu frequency by setting config.txt as following: ```config core_freq_fixed=1 arm_freq=800 arm_freq_min=800 gpu_freq=300 core_freq=300 h264_freq=300 isp_freq=300 v3d_freq=300 hevc_freq=300 sdram_freq=400 gpu_freq_min=300 core_freq_min=300 h264_freq_min=300 isp_freq_min=300 v3d_freq_min=300 hevc_freq_min=300 sdram_freq_min=400 ``` The test source is commit 7d31f578f323 ("Add linux-next specific files for 20251128") from liunx-next branch. Using default defconfig config, and setting: CONFIG_ARM64_SVE=n CONFIG_COMPAT=n CONFIG_COMPAT_32BIT_TIME=n CONFIG_ARM64_PTR_AUTH=n CONFIG_ARM64_GCS=n CONFIG_ARM64_MTE=n CONFIG_SHADOW_CALL_STACK=y CONFIG_SCHED_AUTOGROUP=n CONFIG_CGROUPS=n CONFIG_KVM=n CONFIG_HZ_100=y CONFIG_HZ=100 Thanks very much! Xie Yuanbin