diff options
Diffstat (limited to 'arch/riscv/kernel/unaligned_access_speed.c')
| -rw-r--r-- | arch/riscv/kernel/unaligned_access_speed.c | 321 |
1 files changed, 263 insertions, 58 deletions
diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c index a9a6bcb02acf..b8ba13819d05 100644 --- a/arch/riscv/kernel/unaligned_access_speed.c +++ b/arch/riscv/kernel/unaligned_access_speed.c @@ -6,11 +6,13 @@ #include <linux/cpu.h> #include <linux/cpumask.h> #include <linux/jump_label.h> +#include <linux/kthread.h> #include <linux/mm.h> #include <linux/smp.h> #include <linux/types.h> #include <asm/cpufeature.h> #include <asm/hwprobe.h> +#include <asm/vector.h> #include "copy-unaligned.h" @@ -19,10 +21,15 @@ #define MISALIGNED_BUFFER_ORDER get_order(MISALIGNED_BUFFER_SIZE) #define MISALIGNED_COPY_SIZE ((MISALIGNED_BUFFER_SIZE / 2) - 0x80) -DEFINE_PER_CPU(long, misaligned_access_speed); +DEFINE_PER_CPU(long, misaligned_access_speed) = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN; +DEFINE_PER_CPU(long, vector_misaligned_access) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED; + +static long unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN; +static long unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN; -#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS static cpumask_t fast_misaligned_access; + +#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS static int check_unaligned_access(void *param) { int cpu = smp_processor_id(); @@ -34,9 +41,9 @@ static int check_unaligned_access(void *param) struct page *page = param; void *dst; void *src; - long speed = RISCV_HWPROBE_MISALIGNED_SLOW; + long speed = RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW; - if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_UNKNOWN) + if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) return 0; /* Make an unaligned destination buffer. */ @@ -95,14 +102,14 @@ static int check_unaligned_access(void *param) } if (word_cycles < byte_cycles) - speed = RISCV_HWPROBE_MISALIGNED_FAST; + speed = RISCV_HWPROBE_MISALIGNED_SCALAR_FAST; ratio = div_u64((byte_cycles * 100), word_cycles); pr_info("cpu%d: Ratio of byte access time to unaligned word access is %d.%02d, unaligned accesses are %s\n", cpu, ratio / 100, ratio % 100, - (speed == RISCV_HWPROBE_MISALIGNED_FAST) ? "fast" : "slow"); + (speed == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST) ? "fast" : "slow"); per_cpu(misaligned_access_speed, cpu) = speed; @@ -110,7 +117,7 @@ static int check_unaligned_access(void *param) * Set the value of fast_misaligned_access of a CPU. These operations * are atomic to avoid race conditions. */ - if (speed == RISCV_HWPROBE_MISALIGNED_FAST) + if (speed == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST) cpumask_set_cpu(cpu, &fast_misaligned_access); else cpumask_clear_cpu(cpu, &fast_misaligned_access); @@ -118,7 +125,7 @@ static int check_unaligned_access(void *param) return 0; } -static void check_unaligned_access_nonboot_cpu(void *param) +static void __init check_unaligned_access_nonboot_cpu(void *param) { unsigned int cpu = smp_processor_id(); struct page **pages = param; @@ -127,6 +134,50 @@ static void check_unaligned_access_nonboot_cpu(void *param) check_unaligned_access(pages[cpu]); } +/* Measure unaligned access speed on all CPUs present at boot in parallel. */ +static void __init check_unaligned_access_speed_all_cpus(void) +{ + unsigned int cpu; + unsigned int cpu_count = num_possible_cpus(); + struct page **bufs = kcalloc(cpu_count, sizeof(*bufs), GFP_KERNEL); + + if (!bufs) { + pr_warn("Allocation failure, not measuring misaligned performance\n"); + return; + } + + /* + * Allocate separate buffers for each CPU so there's no fighting over + * cache lines. + */ + for_each_cpu(cpu, cpu_online_mask) { + bufs[cpu] = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER); + if (!bufs[cpu]) { + pr_warn("Allocation failure, not measuring misaligned performance\n"); + goto out; + } + } + + /* Check everybody except 0, who stays behind to tend jiffies. */ + on_each_cpu(check_unaligned_access_nonboot_cpu, bufs, 1); + + /* Check core 0. */ + smp_call_on_cpu(0, check_unaligned_access, bufs[0], true); + +out: + for_each_cpu(cpu, cpu_online_mask) { + if (bufs[cpu]) + __free_pages(bufs[cpu], MISALIGNED_BUFFER_ORDER); + } + + kfree(bufs); +} +#else /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */ +static void __init check_unaligned_access_speed_all_cpus(void) +{ +} +#endif + DEFINE_STATIC_KEY_FALSE(fast_unaligned_access_speed_key); static void modify_unaligned_access_branches(cpumask_t *mask, int weight) @@ -172,7 +223,7 @@ static void set_unaligned_access_static_branches(void) modify_unaligned_access_branches(&fast_and_online, num_online_cpus()); } -static int lock_and_set_unaligned_access_static_branch(void) +static int __init lock_and_set_unaligned_access_static_branch(void) { cpus_read_lock(); set_unaligned_access_static_branches(); @@ -185,20 +236,29 @@ arch_initcall_sync(lock_and_set_unaligned_access_static_branch); static int riscv_online_cpu(unsigned int cpu) { - static struct page *buf; - /* We are already set since the last check */ - if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_UNKNOWN) + if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) { + goto exit; + } else if (unaligned_scalar_speed_param != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) { + per_cpu(misaligned_access_speed, cpu) = unaligned_scalar_speed_param; goto exit; - - buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER); - if (!buf) { - pr_warn("Allocation failure, not measuring misaligned performance\n"); - return -ENOMEM; } - check_unaligned_access(buf); - __free_pages(buf, MISALIGNED_BUFFER_ORDER); +#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS + { + static struct page *buf; + + check_unaligned_access_emulated(NULL); + buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER); + if (!buf) { + pr_warn("Allocation failure, not measuring misaligned performance\n"); + return -ENOMEM; + } + + check_unaligned_access(buf); + __free_pages(buf, MISALIGNED_BUFFER_ORDER); + } +#endif exit: set_unaligned_access_static_branches(); @@ -213,69 +273,214 @@ static int riscv_offline_cpu(unsigned int cpu) return 0; } -/* Measure unaligned access speed on all CPUs present at boot in parallel. */ -static int check_unaligned_access_speed_all_cpus(void) +#ifdef CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS +static void check_vector_unaligned_access(struct work_struct *work __always_unused) { - unsigned int cpu; - unsigned int cpu_count = num_possible_cpus(); - struct page **bufs = kcalloc(cpu_count, sizeof(*bufs), GFP_KERNEL); + int cpu = 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 = RISCV_HWPROBE_MISALIGNED_VECTOR_SLOW; - if (!bufs) { - pr_warn("Allocation failure, not measuring misaligned performance\n"); - return 0; + if (per_cpu(vector_misaligned_access, cpu) != RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN) + return; + + page = 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 = (void *)((unsigned long)page_address(page) | 0x1); + /* Unalign src as well, but differently (off by 1 + 2 = 3). */ + src = dst + (MISALIGNED_BUFFER_SIZE / 2); + src += 2; + word_cycles = -1ULL; + + /* Do a warmup. */ + kernel_vector_begin(); + __riscv_copy_vec_words_unaligned(dst, src, MISALIGNED_COPY_SIZE); + + start_jiffies = jiffies; + while ((now = jiffies) == start_jiffies) + cpu_relax(); + /* - * Allocate separate buffers for each CPU so there's no fighting over - * cache lines. + * For a fixed amount of time, repeatedly try the function, and take + * the best time in cycles as the measurement. */ - for_each_cpu(cpu, cpu_online_mask) { - bufs[cpu] = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER); - if (!bufs[cpu]) { - pr_warn("Allocation failure, not measuring misaligned performance\n"); - goto out; - } + while (time_before(jiffies, now + (1 << MISALIGNED_ACCESS_JIFFIES_LG2))) { + start_cycles = 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 = get_cycles64(); + if ((end_cycles - start_cycles) < word_cycles) + word_cycles = end_cycles - start_cycles; } - /* Check everybody except 0, who stays behind to tend jiffies. */ - on_each_cpu(check_unaligned_access_nonboot_cpu, bufs, 1); + byte_cycles = -1ULL; + __riscv_copy_vec_bytes_unaligned(dst, src, MISALIGNED_COPY_SIZE); + start_jiffies = jiffies; + while ((now = jiffies) == start_jiffies) + cpu_relax(); - /* Check core 0. */ - smp_call_on_cpu(0, check_unaligned_access, bufs[0], true); + while (time_before(jiffies, now + (1 << MISALIGNED_ACCESS_JIFFIES_LG2))) { + start_cycles = get_cycles64(); + /* Ensure the CSR read can't reorder WRT to the copy. */ + mb(); + __riscv_copy_vec_bytes_unaligned(dst, src, MISALIGNED_COPY_SIZE); + /* Ensure the copy ends before the end time is snapped. */ + mb(); + end_cycles = get_cycles64(); + if ((end_cycles - start_cycles) < byte_cycles) + byte_cycles = end_cycles - start_cycles; + } - /* - * 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, riscv_offline_cpu); + kernel_vector_end(); -out: - for_each_cpu(cpu, cpu_online_mask) { - if (bufs[cpu]) - __free_pages(bufs[cpu], MISALIGNED_BUFFER_ORDER); + /* Don't divide by zero. */ + if (!word_cycles || !byte_cycles) { + pr_warn("cpu%d: rdtime lacks granularity needed to measure unaligned vector access speed\n", + cpu); + + goto free; } - kfree(bufs); + if (word_cycles < byte_cycles) + speed = RISCV_HWPROBE_MISALIGNED_VECTOR_FAST; + + ratio = 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 == RISCV_HWPROBE_MISALIGNED_VECTOR_FAST) ? "fast" : "slow"); + + per_cpu(vector_misaligned_access, cpu) = speed; + +free: + __free_pages(page, MISALIGNED_BUFFER_ORDER); +} + +/* Measure unaligned access speed on all CPUs present at boot in parallel. */ +static int __init vec_check_unaligned_access_speed_all_cpus(void *unused __always_unused) +{ + schedule_on_each_cpu(check_vector_unaligned_access); + + return 0; +} +#else /* CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS */ +static int __init vec_check_unaligned_access_speed_all_cpus(void *unused __always_unused) +{ return 0; } +#endif -static int check_unaligned_access_all_cpus(void) +static int riscv_online_cpu_vec(unsigned int cpu) { - bool all_cpus_emulated = check_unaligned_access_emulated_all_cpus(); + if (unaligned_vector_speed_param != RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN) { + per_cpu(vector_misaligned_access, cpu) = unaligned_vector_speed_param; + return 0; + } - if (!all_cpus_emulated) - return check_unaligned_access_speed_all_cpus(); +#ifdef CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS + if (per_cpu(vector_misaligned_access, cpu) != RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN) + return 0; + + check_vector_unaligned_access_emulated(NULL); + check_vector_unaligned_access(NULL); +#endif return 0; } -#else /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */ -static int check_unaligned_access_all_cpus(void) + +static const char * const speed_str[] __initconst = { NULL, NULL, "slow", "fast", "unsupported" }; + +static int __init set_unaligned_scalar_speed_param(char *str) { - check_unaligned_access_emulated_all_cpus(); + if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW])) + unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW; + else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_SCALAR_FAST])) + unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_FAST; + else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_SCALAR_UNSUPPORTED])) + unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_UNSUPPORTED; + else + return -EINVAL; + + return 1; +} +__setup("unaligned_scalar_speed=", set_unaligned_scalar_speed_param); + +static int __init set_unaligned_vector_speed_param(char *str) +{ + if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_VECTOR_SLOW])) + unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_SLOW; + else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_VECTOR_FAST])) + unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_FAST; + else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED])) + unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED; + else + return -EINVAL; + + return 1; +} +__setup("unaligned_vector_speed=", set_unaligned_vector_speed_param); + +static int __init check_unaligned_access_all_cpus(void) +{ + int cpu; + + if (unaligned_scalar_speed_param != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) { + pr_info("scalar unaligned access speed set to '%s' (%lu) by command line\n", + speed_str[unaligned_scalar_speed_param], unaligned_scalar_speed_param); + for_each_online_cpu(cpu) + per_cpu(misaligned_access_speed, cpu) = unaligned_scalar_speed_param; + } else if (!check_unaligned_access_emulated_all_cpus()) { + check_unaligned_access_speed_all_cpus(); + } + + if (unaligned_vector_speed_param != RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN) { + if (!has_vector() && + unaligned_vector_speed_param != RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED) { + pr_warn("vector support is not available, ignoring unaligned_vector_speed=%s\n", + speed_str[unaligned_vector_speed_param]); + } else { + pr_info("vector unaligned access speed set to '%s' (%lu) by command line\n", + speed_str[unaligned_vector_speed_param], unaligned_vector_speed_param); + } + } + + if (!has_vector()) + unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED; + + if (unaligned_vector_speed_param != RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN) { + for_each_online_cpu(cpu) + per_cpu(vector_misaligned_access, cpu) = unaligned_vector_speed_param; + } else if (!check_vector_unaligned_access_emulated_all_cpus() && + 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"); + } + + /* + * 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, riscv_offline_cpu); + cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "riscv:online", + riscv_online_cpu_vec, NULL); return 0; } -#endif arch_initcall(check_unaligned_access_all_cpus); |