Tool to monitor CPU core frequencies

Author: sahmad98

core_frequency.py

@@ -0,0 +1,104 @@
+#!/usr/bin/env python
+
+'''
+core_frequency.py - Low overhead BPF Tool to monitor core frequencies.
+Author: Saleem Ahmad (saleem.iitg[@]gmail.com)
+
+Usage: ./core_frequency.py [-s 1] [-t 2.5]
+
+NOTE: For Reference TSC Frequency, put the value of frequency in Model Name of
+lscpu output, or read 0x16 leaf of CPUID. For more information read about
+cpuid instruction in x86
+'''
+
+from bcc import BPF, PerfType, PerfHWConfig, utils, PerfSWConfig
+from optparse import OptionParser
+
+parser = OptionParser()
+parser.add_option('-s', '--sample-freq', dest='sample_freq', help='Frequency Sample Rate in Hz', type=int, default=1)
+parser.add_option('-t', '--tsc-freq', dest='tsc_freq', help='Reference Clock Frequency in GHz (see lscpu or cpuid)', type=float, default=2.5)
+(option, args) = parser.parse_args()
+
+code = '''
+# include <linux/bpf.h>
+# include <uapi/linux/bpf_perf_event.h>
+# include <uapi/linux/ptrace.h>
+
+/*
+- Structure to hold the last sample data as well as to output
+differential data via perf event buffer.
+*/
+struct PerfData {
+    u64 cycles;
+    u64 ref_cycles;
+};
+
+// Perf Events array
+BPF_PERF_ARRAY(cycles, MAX_CPUS);
+BPF_PERF_ARRAY(ref_cycles, MAX_CPUS);
+
+// Per CPU array to store the last samples.
+BPF_PERCPU_ARRAY(last_sample, struct PerfData, MAX_CPUS);
+
+// Perf Ouptut Buffer
+BPF_PERF_OUTPUT(output);
+
+void get_perf_counters(struct bpf_perf_event_data* ctx) {
+    u32 cpu = bpf_get_smp_processor_id();
+    /*
+    NOTE: Use bpf_perf_event_value is recommended over
+    bpf_perf_event_read or map.perf_read() due to
+    issues in ABI. map.perf_read_value() need to be
+    implemented in future.
+    */
+    u64 cyc = cycles.perf_read(cpu);
+    u64 ref = ref_cycles.perf_read(cpu);
+
+    struct PerfData result;
+    struct PerfData* ptr = last_sample.lookup(&cpu);
+
+    if (ptr) {
+        result.cycles = cyc - ptr->cycles;
+        result.ref_cycles = ref - ptr->ref_cycles;
+        ptr->cycles = cyc;
+        ptr->ref_cycles = ref;
+        output.perf_submit(ctx, &result, sizeof(struct PerfData));
+    } else {
+        result.cycles = cyc;
+        result.ref_cycles = ref;
+        last_sample.insert(&cpu, &result);
+    }
+}
+'''
+
+max_cpus = len(utils.get_online_cpus())
+b = BPF(text=code, cflags=['-DMAX_CPUS=%s' % str(max_cpus)])
+
+# Cycles and Ref Cycles counters are required to measure frequency.
+b['cycles'].open_perf_event(PerfType.HARDWARE, PerfHWConfig.CPU_CYCLES)
+b['ref_cycles'].open_perf_event(PerfType.HARDWARE, PerfHWConfig.REF_CPU_CYCLES)
+
+# A dummy perf event which will get triggered at every Sample Frequency.
+b.attach_perf_event(ev_type=PerfType.SOFTWARE,
+    ev_config=PerfSWConfig.CPU_CLOCK,
+    fn_name='get_perf_counters',
+    sample_freq=option.sample_freq)
+
+
+def print_data(cpu, data, size):
+    e = b["output"].event(data)
+    print "%-4d %-16d %-16d %-16.2f" % (cpu, e.cycles, 
+        e.ref_cycles, 
+        e.cycles * option.tsc_freq / e.ref_cycles)
+
+
+print "Counters Data"
+print "%-4s %-16s %-16s %-16s" % ('CPU', 'CLOCK', 'REF-CYCLES', 'FREQ')
+
+b['output'].open_perf_buffer(print_data)
+
+while True:
+    try:
+        b.perf_buffer_poll()
+    except KeyboardInterrupt:
+        exit()