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(pool-108-26-179-17.bstnma.fios.verizon.net. [108.26.179.17]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f9ebbb2a7csm68150235ad.256.2024.06.24.17.51.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Jun 2024 17:52:00 -0700 (PDT) From: Jesse Taube To: linux-riscv@lists.infradead.org Cc: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= , Evan Green , Andrew Jones , Jesse Taube , Charlie Jenkins , Xiao Wang , Andy Chiu , Eric Biggers , Greentime Hu , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Heiko Stuebner , Costa Shulyupin , Andrew Morton , Baoquan He , Anup Patel , Zong Li , Sami Tolvanen , Ben Dooks , Alexandre Ghiti , "Gustavo A. R. Silva" , Erick Archer , Joel Granados , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org Subject: [PATCH v3 7/8] RISC-V: Report vector unaligned access speed hwprobe Date: Mon, 24 Jun 2024 20:50:00 -0400 Message-ID: <20240625005001.37901-8-jesse@rivosinc.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240625005001.37901-1-jesse@rivosinc.com> References: <20240625005001.37901-1-jesse@rivosinc.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Detect if vector misaligned accesses are faster or slower than equivalent vector byte accesses. This is useful for usermode to know whether vector byte accesses or vector misaligned accesses have a better bandwidth for operations like memcpy. Signed-off-by: Jesse Taube --- V1 -> V2: - Add Kconfig options - Add WORD_EEW to vec-copy-unaligned.S V2 -> V3: - Remove unnecessary comment - Remove local_irq_enable --- arch/riscv/Kconfig | 18 +++ arch/riscv/kernel/Makefile | 3 +- arch/riscv/kernel/copy-unaligned.h | 5 + arch/riscv/kernel/sys_hwprobe.c | 6 + arch/riscv/kernel/unaligned_access_speed.c | 132 ++++++++++++++++++++- arch/riscv/kernel/vec-copy-unaligned.S | 58 +++++++++ 6 files changed, 219 insertions(+), 3 deletions(-) create mode 100644 arch/riscv/kernel/vec-copy-unaligned.S diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index ffbe0fdd7fb3..6f9fd3748916 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -807,6 +807,24 @@ config RISCV_PROBE_VECTOR_UNALIGNED_ACCESS will dynamically determine the speed of vector unaligned accesses on the underlying system if they are supported. =20 +config RISCV_SLOW_VEC_UNALIGNED_ACCESS + bool "Assume the system supports slow vector unaligned memory accesses" + depends on NONPORTABLE + help + Assume that the system supports slow vector unaligned memory accesses. = The + kernel and userspace programs may not be able to run at all on systems + that do not support unaligned memory accesses. + +config RISCV_EFFICIENT_VEC_UNALIGNED_ACCESS + bool "Assume the system supports fast vector unaligned memory accesses" + depends on NONPORTABLE + help + Assume that the system supports fast vector unaligned memory accesses. = When + enabled, this option improves the performance of the kernel on such + systems. However, the kernel and userspace programs will run much more + slowly, or will not be able to run at all, on systems that do not + support efficient unaligned memory accesses. + endchoice =20 endmenu # "Platform type" diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index 5b243d46f4b1..291935a084d5 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -64,7 +64,8 @@ obj-$(CONFIG_MMU) +=3D vdso.o vdso/ =20 obj-$(CONFIG_RISCV_MISALIGNED) +=3D traps_misaligned.o obj-$(CONFIG_RISCV_MISALIGNED) +=3D unaligned_access_speed.o -obj-$(CONFIG_RISCV_PROBE_UNALIGNED_ACCESS) +=3D copy-unaligned.o +obj-$(CONFIG_RISCV_PROBE_UNALIGNED_ACCESS) +=3D copy-unaligned.o +obj-$(CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS) +=3D vec-copy-unaligned.o =20 obj-$(CONFIG_FPU) +=3D fpu.o obj-$(CONFIG_FPU) +=3D kernel_mode_fpu.o diff --git a/arch/riscv/kernel/copy-unaligned.h b/arch/riscv/kernel/copy-un= aligned.h index e3d70d35b708..85d4d11450cb 100644 --- a/arch/riscv/kernel/copy-unaligned.h +++ b/arch/riscv/kernel/copy-unaligned.h @@ -10,4 +10,9 @@ void __riscv_copy_words_unaligned(void *dst, const void *src, size_t size); void __riscv_copy_bytes_unaligned(void *dst, const void *src, size_t size); =20 +#ifdef CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS +void __riscv_copy_vec_words_unaligned(void *dst, const void *src, size_t s= ize); +void __riscv_copy_vec_bytes_unaligned(void *dst, const void *src, size_t s= ize); +#endif + #endif /* __RISCV_KERNEL_COPY_UNALIGNED_H */ diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprob= e.c index 5b78ea5a84d1..46de3f145154 100644 --- a/arch/riscv/kernel/sys_hwprobe.c +++ b/arch/riscv/kernel/sys_hwprobe.c @@ -221,6 +221,12 @@ static u64 hwprobe_vec_misaligned(const struct cpumask= *cpus) #else static u64 hwprobe_vec_misaligned(const struct cpumask *cpus) { + if (IS_ENABLED(CONFIG_RISCV_EFFICIENT_VEC_UNALIGNED_ACCESS)) + return RISCV_HWPROBE_VEC_MISALIGNED_FAST; + + if (IS_ENABLED(CONFIG_RISCV_SLOW_VEC_UNALIGNED_ACCESS)) + return RISCV_HWPROBE_VEC_MISALIGNED_SLOW; + return RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN; } #endif diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel= /unaligned_access_speed.c index 8489e012cf23..a2a8f948500b 100644 --- a/arch/riscv/kernel/unaligned_access_speed.c +++ b/arch/riscv/kernel/unaligned_access_speed.c @@ -8,9 +8,11 @@ #include #include #include +#include #include #include #include +#include =20 #include "copy-unaligned.h" =20 @@ -267,9 +269,129 @@ static int check_unaligned_access_speed_all_cpus(void) } #endif =20 +#ifdef CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS +static void check_vector_unaligned_access(struct work_struct *unused) +{ + int cpu =3D smp_processor_id(); + u64 start_cycles, end_cycles; + u64 word_cycles; + u64 byte_cycles; + int ratio; + unsigned long start_jiffies, now; + struct page *page; + void *dst; + void *src; + long speed =3D RISCV_HWPROBE_VEC_MISALIGNED_SLOW; + + if (per_cpu(vector_misaligned_access, cpu) !=3D RISCV_HWPROBE_VEC_MISALIG= NED_SLOW) + return; + + page =3D alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER); + if (!page) { + pr_warn("Allocation failure, not measuring vector misaligned performance= \n"); + return; + } + + /* Make an unaligned destination buffer. */ + dst =3D (void *)((unsigned long)page_address(page) | 0x1); + /* Unalign src as well, but differently (off by 1 + 2 =3D 3). */ + src =3D dst + (MISALIGNED_BUFFER_SIZE / 2); + src +=3D 2; + word_cycles =3D -1ULL; + + /* Do a warmup. */ + kernel_vector_begin(); + __riscv_copy_vec_words_unaligned(dst, src, MISALIGNED_COPY_SIZE); + + start_jiffies =3D jiffies; + while ((now =3D jiffies) =3D=3D start_jiffies) + cpu_relax(); + + /* + * For a fixed amount of time, repeatedly try the function, and take + * the best time in cycles as the measurement. + */ + while (time_before(jiffies, now + (1 << MISALIGNED_ACCESS_JIFFIES_LG2))) { + start_cycles =3D get_cycles64(); + /* Ensure the CSR read can't reorder WRT to the copy. */ + mb(); + __riscv_copy_vec_words_unaligned(dst, src, MISALIGNED_COPY_SIZE); + /* Ensure the copy ends before the end time is snapped. */ + mb(); + end_cycles =3D get_cycles64(); + if ((end_cycles - start_cycles) < word_cycles) + word_cycles =3D end_cycles - start_cycles; + } + + byte_cycles =3D -1ULL; + __riscv_copy_vec_bytes_unaligned(dst, src, MISALIGNED_COPY_SIZE); + start_jiffies =3D jiffies; + while ((now =3D jiffies) =3D=3D start_jiffies) + cpu_relax(); + + while (time_before(jiffies, now + (1 << MISALIGNED_ACCESS_JIFFIES_LG2))) { + start_cycles =3D get_cycles64(); + mb(); + __riscv_copy_vec_bytes_unaligned(dst, src, MISALIGNED_COPY_SIZE); + mb(); + end_cycles =3D get_cycles64(); + if ((end_cycles - start_cycles) < byte_cycles) + byte_cycles =3D end_cycles - start_cycles; + } + + kernel_vector_end(); + + /* Don't divide by zero. */ + if (!word_cycles || !byte_cycles) { + pr_warn("cpu%d: rdtime lacks granularity needed to measure unaligned vec= tor access speed\n", + cpu); + + return; + } + + if (word_cycles < byte_cycles) + speed =3D RISCV_HWPROBE_VEC_MISALIGNED_FAST; + + ratio =3D div_u64((byte_cycles * 100), word_cycles); + pr_info("cpu%d: Ratio of vector byte access time to vector unaligned word= access is %d.%02d, unaligned accesses are %s\n", + cpu, + ratio / 100, + ratio % 100, + (speed =3D=3D RISCV_HWPROBE_VEC_MISALIGNED_FAST) ? "fast" : "slow"); + + per_cpu(vector_misaligned_access, cpu) =3D speed; +} + +static int riscv_online_cpu_vec(unsigned int cpu) +{ + check_vector_unaligned_access(NULL); + return 0; +} + +/* Measure unaligned access speed on all CPUs present at boot in parallel.= */ +static int vec_check_unaligned_access_speed_all_cpus(void *unused) +{ + schedule_on_each_cpu(check_vector_unaligned_access); + + /* + * Setup hotplug callbacks for any new CPUs that come online or go + * offline. + */ + cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "riscv:online", + riscv_online_cpu_vec, NULL); + + return 0; +} +#else /* CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS */ +static int vec_check_unaligned_access_speed_all_cpus(void *unused) +{ + return 0; +} +#endif + static int check_unaligned_access_all_cpus(void) { - bool all_cpus_emulated; + bool all_cpus_emulated, all_cpus_vec_supported; int cpu; =20 if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICCLSM)) { @@ -285,7 +407,13 @@ static int check_unaligned_access_all_cpus(void) } =20 all_cpus_emulated =3D check_unaligned_access_emulated_all_cpus(); - check_vector_unaligned_access_emulated_all_cpus(); + all_cpus_vec_supported =3D check_vector_unaligned_access_emulated_all_cpu= s(); + + if (all_cpus_vec_supported && + IS_ENABLED(CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS)) { + kthread_run(vec_check_unaligned_access_speed_all_cpus, + NULL, "vec_check_unaligned_access_speed_all_cpus"); + } =20 if (!all_cpus_emulated) return check_unaligned_access_speed_all_cpus(); diff --git a/arch/riscv/kernel/vec-copy-unaligned.S b/arch/riscv/kernel/vec= -copy-unaligned.S new file mode 100644 index 000000000000..e5bc94917e60 --- /dev/null +++ b/arch/riscv/kernel/vec-copy-unaligned.S @@ -0,0 +1,58 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2024 Rivos Inc. */ + +#include +#include +#include + + .text + +#define WORD_EEW 32 + +#define WORD_SEW CONCATENATE(e, WORD_EEW) +#define VEC_L CONCATENATE(vle, WORD_EEW).v +#define VEC_S CONCATENATE(vle, WORD_EEW).v + +/* void __riscv_copy_vec_words_unaligned(void *, const void *, size_t) */ +/* Performs a memcpy without aligning buffers, using word loads and stores= . */ +/* Note: The size is truncated to a multiple of WORD_EEW */ +SYM_FUNC_START(__riscv_copy_vec_words_unaligned) + andi a4, a2, ~(WORD_EEW-1) + beqz a4, 2f + add a3, a1, a4 + .option push + .option arch, +zve32x +1: + vsetivli t0, 8, WORD_SEW, m8, ta, ma + VEC_L v0, (a1) + VEC_S v0, (a0) + addi a0, a0, WORD_EEW + addi a1, a1, WORD_EEW + bltu a1, a3, 1b + +2: + .option pop + ret +SYM_FUNC_END(__riscv_copy_vec_words_unaligned) + +/* void __riscv_copy_vec_bytes_unaligned(void *, const void *, size_t) */ +/* Performs a memcpy without aligning buffers, using only byte accesses. */ +/* Note: The size is truncated to a multiple of 8 */ +SYM_FUNC_START(__riscv_copy_vec_bytes_unaligned) + andi a4, a2, ~(8-1) + beqz a4, 2f + add a3, a1, a4 + .option push + .option arch, +zve32x +1: + vsetivli t0, 8, e8, m8, ta, ma + vle8.v v0, (a1) + vse8.v v0, (a0) + addi a0, a0, 8 + addi a1, a1, 8 + bltu a1, a3, 1b + +2: + .option pop + ret +SYM_FUNC_END(__riscv_copy_vec_bytes_unaligned) --=20 2.45.2