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79 lines
1.9 KiB
79 lines
1.9 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* Manage affinity to optimize IPIs inside the kernel perf API. */ |
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#define _GNU_SOURCE 1 |
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#include <sched.h> |
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#include <stdlib.h> |
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#include <linux/bitmap.h> |
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#include <linux/zalloc.h> |
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#include "perf.h" |
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#include "cpumap.h" |
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#include "affinity.h" |
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static int get_cpu_set_size(void) |
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{ |
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int sz = cpu__max_cpu().cpu + 8 - 1; |
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/* |
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* sched_getaffinity doesn't like masks smaller than the kernel. |
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* Hopefully that's big enough. |
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*/ |
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if (sz < 4096) |
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sz = 4096; |
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return sz / 8; |
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} |
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int affinity__setup(struct affinity *a) |
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{ |
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int cpu_set_size = get_cpu_set_size(); |
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a->orig_cpus = bitmap_zalloc(cpu_set_size * 8); |
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if (!a->orig_cpus) |
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return -1; |
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sched_getaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus); |
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a->sched_cpus = bitmap_zalloc(cpu_set_size * 8); |
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if (!a->sched_cpus) { |
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zfree(&a->orig_cpus); |
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return -1; |
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} |
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bitmap_zero((unsigned long *)a->sched_cpus, cpu_set_size); |
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a->changed = false; |
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return 0; |
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} |
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/* |
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* perf_event_open does an IPI internally to the target CPU. |
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* It is more efficient to change perf's affinity to the target |
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* CPU and then set up all events on that CPU, so we amortize |
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* CPU communication. |
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*/ |
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void affinity__set(struct affinity *a, int cpu) |
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{ |
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int cpu_set_size = get_cpu_set_size(); |
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if (cpu == -1) |
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return; |
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a->changed = true; |
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set_bit(cpu, a->sched_cpus); |
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/* |
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* We ignore errors because affinity is just an optimization. |
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* This could happen for example with isolated CPUs or cpusets. |
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* In this case the IPIs inside the kernel's perf API still work. |
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*/ |
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sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->sched_cpus); |
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clear_bit(cpu, a->sched_cpus); |
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} |
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static void __affinity__cleanup(struct affinity *a) |
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{ |
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int cpu_set_size = get_cpu_set_size(); |
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if (a->changed) |
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sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus); |
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zfree(&a->sched_cpus); |
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zfree(&a->orig_cpus); |
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} |
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void affinity__cleanup(struct affinity *a) |
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{ |
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if (a != NULL) |
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__affinity__cleanup(a); |
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}
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