/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com * Copyright (c) 2015 BMW Car IT GmbH * * This program is free software; you can redistribute it and/or * modify it under the terms of version 2 of the GNU General Public * License as published by the Free Software Foundation. */ #include #include #include #include "bpf_helpers.h" #define MAX_ENTRIES 20 #define MAX_CPU 4 /* We need to stick to static allocated memory (an array instead of * hash table) because managing dynamic memory from the * trace_preempt_[on|off] tracepoints hooks is not supported. */ struct bpf_map_def SEC("maps") my_map = { .type = BPF_MAP_TYPE_ARRAY, .key_size = sizeof(int), .value_size = sizeof(u64), .max_entries = MAX_CPU, }; SEC("kprobe/trace_preempt_off") int bpf_prog1(struct pt_regs *ctx) { int cpu = bpf_get_smp_processor_id(); u64 *ts = bpf_map_lookup_elem(&my_map, &cpu); if (ts) *ts = bpf_ktime_get_ns(); return 0; } static unsigned int log2(unsigned int v) { unsigned int r; unsigned int shift; r = (v > 0xFFFF) << 4; v >>= r; shift = (v > 0xFF) << 3; v >>= shift; r |= shift; shift = (v > 0xF) << 2; v >>= shift; r |= shift; shift = (v > 0x3) << 1; v >>= shift; r |= shift; r |= (v >> 1); return r; } static unsigned int log2l(unsigned long v) { unsigned int hi = v >> 32; if (hi) return log2(hi) + 32; else return log2(v); } struct bpf_map_def SEC("maps") my_lat = { .type = BPF_MAP_TYPE_ARRAY, .key_size = sizeof(int), .value_size = sizeof(long), .max_entries = MAX_CPU * MAX_ENTRIES, }; SEC("kprobe/trace_preempt_on") int bpf_prog2(struct pt_regs *ctx) { u64 *ts, cur_ts, delta; int key, cpu; long *val; cpu = bpf_get_smp_processor_id(); ts = bpf_map_lookup_elem(&my_map, &cpu); if (!ts) return 0; cur_ts = bpf_ktime_get_ns(); delta = log2l(cur_ts - *ts); if (delta > MAX_ENTRIES - 1) delta = MAX_ENTRIES - 1; key = cpu * MAX_ENTRIES + delta; val = bpf_map_lookup_elem(&my_lat, &key); if (val) __sync_fetch_and_add((long *)val, 1); return 0; } char _license[] SEC("license") = "GPL"; u32 _version SEC("version") = LINUX_VERSION_CODE; method='get' action='/cgit.cgi/linux/net-next.git/log/tools/perf/util/event.h'>
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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2017-01-30 19:27:10 -0500
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2017-01-31 09:13:49 -0500
commit79c6f448c8b79c321e4a1f31f98194e4f6b6cae7 (patch)
tree370efda701f03cccf21e02bb1fdd3b852547d75c /tools/perf/util/event.h
parent0c744ea4f77d72b3dcebb7a8f2684633ec79be88 (diff)
tracing: Fix hwlat kthread migration
The hwlat tracer creates a kernel thread at start of the tracer. It is pinned to a single CPU and will move to the next CPU after each period of running. If the user modifies the migration thread's affinity, it will not change after that happens. The original code created the thread at the first instance it was called, but later was changed to destroy the thread after the tracer was finished, and would not be created until the next instance of the tracer was established. The code that initialized the affinity was only called on the initial instantiation of the tracer. After that, it was not initialized, and the previous affinity did not match the current newly created one, making it appear that the user modified the thread's affinity when it did not, and the thread failed to migrate again. Cc: stable@vger.kernel.org Fixes: 0330f7aa8ee6 ("tracing: Have hwlat trace migrate across tracing_cpumask CPUs") Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'tools/perf/util/event.h')