Fix CPU load reporting independent of scheduler used.
- Sample CPU usage data from kern.cp_times, this makes for a far more accurate and scheduler independent algorithm. - Rip out the process list scraping that is no longer required. - Don't update CPU usage sampling on every request, but every 15s instead. This makes it impossible for an attacker to hide the CPU load by triggering 4 samplings in short succession when the system is idle. - After reaching the steady-state, the system will always report the average CPU load of the last 60 sampled seconds. - Untangling of call graph. PR: kern/130222 Tested by: Julian Dunn <jdunn@aquezada.com> Gustau Pérez <gperez@entel.upc.edu> Jürgen Weiß <weiss@uni-mainz.de> MFC after: 2 weeks I'm unsure if some MIB standard states this must be the load average for, eg. 300s, it looks like net-snmp isn't even bothering to implement the CPU load reporting at all.
This commit is contained in:
Ulrich Spörlein
parent
c2ab553ee5
commit
ac203a768d
@ -56,19 +56,15 @@
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struct processor_entry {
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int32_t index;
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const struct asn_oid *frwId;
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int32_t load;
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int32_t load; /* average cpu usage */
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int32_t sample_cnt; /* number of usage samples */
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int32_t cur_sample_idx; /* current valid sample */
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TAILQ_ENTRY(processor_entry) link;
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u_char cpu_no; /* which cpu, counted from 0 */
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pid_t idle_pid; /* PID of idle process for this CPU */
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/* the samples from the last minute, as required by MIB */
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double samples[MAX_CPU_SAMPLES];
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/* current sample to fill in next time, must be < MAX_CPU_SAMPLES */
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uint32_t cur_sample_idx;
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/* number of useful samples */
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uint32_t sample_cnt;
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long states[MAX_CPU_SAMPLES][CPUSTATES];
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};
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TAILQ_HEAD(processor_tbl, processor_entry);
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@ -82,65 +78,78 @@ static int32_t detected_processor_count;
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/* sysctlbyname(hw.ncpu) */
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static int hw_ncpu;
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/* sysctlbyname(kern.{ccpu,fscale}) */
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static fixpt_t ccpu;
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static int fscale;
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/* tick of PDU where we have refreshed the processor table last */
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static uint64_t proctbl_tick;
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/* sysctlbyname(kern.cp_times) */
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static int cpmib[2];
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static size_t cplen;
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/* periodic timer used to get cpu load stats */
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static void *cpus_load_timer;
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/*
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* Average the samples. The entire algorithm seems to be wrong XXX.
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/**
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* Returns the CPU usage of a given processor entry.
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*
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* It needs at least two cp_times "tick" samples to calculate a delta and
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* thus, the usage over the sampling period.
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*/
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static int
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get_avg_load(struct processor_entry *e)
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{
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u_int i;
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double sum = 0.0;
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u_int i, oldest;
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long delta = 0;
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double usage = 0.0;
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assert(e != NULL);
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if (e->sample_cnt == 0)
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/* Need two samples to perform delta calculation. */
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if (e->sample_cnt <= 1)
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return (0);
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for (i = 0; i < e->sample_cnt; i++)
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sum += e->samples[i];
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/* Oldest usable index, we wrap around. */
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if (e->sample_cnt == MAX_CPU_SAMPLES)
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oldest = (e->cur_sample_idx + 1) % MAX_CPU_SAMPLES;
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else
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oldest = 0;
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return ((int)floor((double)sum/(double)e->sample_cnt));
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}
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/* Sum delta for all states. */
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for (i = 0; i < CPUSTATES; i++) {
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delta += e->states[e->cur_sample_idx][i];
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delta -= e->states[oldest][i];
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}
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if (delta == 0)
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return 0;
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/*
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* Stolen from /usr/src/bin/ps/print.c. The idle process should never
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* be swapped out :-)
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*/
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static double
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processor_getpcpu(struct kinfo_proc *ki_p)
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{
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/* Take idle time from the last element and convert to
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* percent usage by contrasting with total ticks delta. */
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usage = (double)(e->states[e->cur_sample_idx][CPUSTATES-1] -
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e->states[oldest][CPUSTATES-1]) / delta;
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usage = 100 - (usage * 100);
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HRDBG("CPU no. %d, delta ticks %ld, pct usage %.2f", e->cpu_no,
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delta, usage);
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if (ccpu == 0 || fscale == 0)
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return (0.0);
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#define fxtofl(fixpt) ((double)(fixpt) / fscale)
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return (100.0 * fxtofl(ki_p->ki_pctcpu) /
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(1.0 - exp(ki_p->ki_swtime * log(fxtofl(ccpu)))));
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return ((int)(usage));
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}
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/**
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* Save a new sample
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* Save a new sample to proc entry and get the average usage.
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*
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* Samples are stored in a ringbuffer from 0..(MAX_CPU_SAMPLES-1)
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*/
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static void
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save_sample(struct processor_entry *e, struct kinfo_proc *kp)
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save_sample(struct processor_entry *e, long *cp_times)
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{
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int i;
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e->samples[e->cur_sample_idx] = 100.0 - processor_getpcpu(kp);
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e->load = get_avg_load(e);
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e->cur_sample_idx = (e->cur_sample_idx + 1) % MAX_CPU_SAMPLES;
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for (i = 0; cp_times != NULL && i < CPUSTATES; i++)
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e->states[e->cur_sample_idx][i] = cp_times[i];
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if (++e->sample_cnt > MAX_CPU_SAMPLES)
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e->sample_cnt++;
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if (e->sample_cnt > MAX_CPU_SAMPLES)
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e->sample_cnt = MAX_CPU_SAMPLES;
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HRDBG("sample count for CPU no. %d went to %d", e->cpu_no, e->sample_cnt);
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e->load = get_avg_load(e);
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}
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/**
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@ -178,8 +187,9 @@ proc_create_entry(u_int cpu_no, struct device_map_entry *map)
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entry->index = map->hrIndex;
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entry->load = 0;
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entry->sample_cnt = 0;
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entry->cur_sample_idx = -1;
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entry->cpu_no = (u_char)cpu_no;
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entry->idle_pid = 0;
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entry->frwId = &oid_zeroDotZero; /* unknown id FIXME */
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INSERT_OBJECT_INT(entry, &processor_tbl);
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@ -190,65 +200,12 @@ proc_create_entry(u_int cpu_no, struct device_map_entry *map)
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return (entry);
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}
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/**
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* Get the PIDs for the idle processes of the CPUs.
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*/
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static void
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processor_get_pids(void)
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{
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struct kinfo_proc *plist, *kp;
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int i;
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int nproc;
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int cpu;
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int nchars;
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struct processor_entry *entry;
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plist = kvm_getprocs(hr_kd, KERN_PROC_ALL, 0, &nproc);
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if (plist == NULL || nproc < 0) {
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syslog(LOG_ERR, "hrProcessor: kvm_getprocs() failed: %m");
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return;
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}
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for (i = 0, kp = plist; i < nproc; i++, kp++) {
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if (!IS_KERNPROC(kp))
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continue;
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if (strcmp(kp->ki_comm, "idle") == 0) {
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/* single processor system */
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cpu = 0;
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} else if (sscanf(kp->ki_comm, "idle: cpu%d%n", &cpu, &nchars)
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== 1 && (u_int)nchars == strlen(kp->ki_comm)) {
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/* MP system */
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} else
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/* not an idle process */
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continue;
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HRDBG("'%s' proc with pid %d is on CPU #%d (last on #%d)",
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kp->ki_comm, kp->ki_pid, kp->ki_oncpu, kp->ki_lastcpu);
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TAILQ_FOREACH(entry, &processor_tbl, link)
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if (entry->cpu_no == kp->ki_lastcpu)
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break;
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if (entry == NULL) {
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/* create entry on non-ACPI systems */
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if ((entry = proc_create_entry(cpu, NULL)) == NULL)
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continue;
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detected_processor_count++;
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}
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entry->idle_pid = kp->ki_pid;
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HRDBG("CPU no. %d with SNMP index=%d has idle PID %d",
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entry->cpu_no, entry->index, entry->idle_pid);
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save_sample(entry, kp);
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}
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}
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/**
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* Scan the device map table for CPUs and create an entry into the
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* processor table for each CPU. Then fetch the idle PIDs for all CPUs.
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* processor table for each CPU.
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*
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* Make sure that the number of processors announced by the kernel hw.ncpu
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* is equal to the number of processors we have found in the device table.
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*/
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static void
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create_proc_table(void)
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@ -256,6 +213,7 @@ create_proc_table(void)
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struct device_map_entry *map;
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struct processor_entry *entry;
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int cpu_no;
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size_t len;
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detected_processor_count = 0;
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@ -265,7 +223,7 @@ create_proc_table(void)
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* If not, no entries will be present in the hrProcessor Table.
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*
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* For non-ACPI system the processors are not in the device table,
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* therefor insert them when getting the idle pids. XXX
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* therefore insert them after checking hw.ncpu.
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*/
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STAILQ_FOREACH(map, &device_map, link)
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if (strncmp(map->name_key, "cpu", strlen("cpu")) == 0 &&
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@ -283,9 +241,34 @@ create_proc_table(void)
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detected_processor_count++;
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}
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HRDBG("%d CPUs detected", detected_processor_count);
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len = sizeof(hw_ncpu);
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if (sysctlbyname("hw.ncpu", &hw_ncpu, &len, NULL, 0) == -1 ||
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len != sizeof(hw_ncpu)) {
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syslog(LOG_ERR, "hrProcessorTable: sysctl(hw.ncpu) failed");
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hw_ncpu = 0;
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}
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HRDBG("%d CPUs detected via device table; hw.ncpu is %d",
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detected_processor_count, hw_ncpu);
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/* XXX Can happen on non-ACPI systems? Create entries by hand. */
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for (; detected_processor_count < hw_ncpu; detected_processor_count++)
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proc_create_entry(detected_processor_count, NULL);
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len = 2;
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if (sysctlnametomib("kern.cp_times", cpmib, &len)) {
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syslog(LOG_ERR, "hrProcessorTable: sysctlnametomib(kern.cp_times) failed");
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cpmib[0] = 0;
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cpmib[1] = 0;
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cplen = 0;
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} else if (sysctl(cpmib, 2, NULL, &len, NULL, 0)) {
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syslog(LOG_ERR, "hrProcessorTable: sysctl(kern.cp_times) length query failed");
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cplen = 0;
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} else {
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cplen = len / sizeof(long);
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}
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HRDBG("%zu entries for kern.cp_times", cplen);
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processor_get_pids();
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}
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/**
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@ -306,78 +289,6 @@ free_proc_table(void)
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detected_processor_count = 0;
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}
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/**
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* Init the things for hrProcessorTable.
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* Scan the device table for processor entries.
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*/
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void
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init_processor_tbl(void)
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{
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size_t len;
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/* get various parameters from the kernel */
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len = sizeof(ccpu);
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if (sysctlbyname("kern.ccpu", &ccpu, &len, NULL, 0) == -1) {
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syslog(LOG_ERR, "hrProcessorTable: sysctl(kern.ccpu) failed");
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ccpu = 0;
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}
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len = sizeof(fscale);
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if (sysctlbyname("kern.fscale", &fscale, &len, NULL, 0) == -1) {
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syslog(LOG_ERR, "hrProcessorTable: sysctl(kern.fscale) failed");
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fscale = 0;
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}
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/* create the initial processor table */
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create_proc_table();
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}
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/**
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* Finalization routine for hrProcessorTable.
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* It destroys the lists and frees any allocated heap memory.
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*/
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void
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fini_processor_tbl(void)
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{
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if (cpus_load_timer != NULL) {
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timer_stop(cpus_load_timer);
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cpus_load_timer = NULL;
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}
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free_proc_table();
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}
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/**
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* Make sure that the number of processors announced by the kernel hw.ncpu
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* is equal to the number of processors we have found in the device table.
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* If they differ rescan the device table.
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*/
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static void
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processor_refill_tbl(void)
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{
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HRDBG("hw_ncpu=%d detected_processor_count=%d", hw_ncpu,
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detected_processor_count);
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if (hw_ncpu <= 0) {
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size_t size = sizeof(hw_ncpu);
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if (sysctlbyname("hw.ncpu", &hw_ncpu, &size, NULL, 0) == -1 ||
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size != sizeof(hw_ncpu)) {
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syslog(LOG_ERR, "hrProcessorTable: "
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"sysctl(hw.ncpu) failed: %m");
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hw_ncpu = 0;
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return;
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}
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}
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if (hw_ncpu != detected_processor_count) {
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free_proc_table();
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create_proc_table();
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}
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}
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/**
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* Refresh all values in the processor table. We call this once for
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* every PDU that accesses the table.
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@ -386,37 +297,23 @@ static void
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refresh_processor_tbl(void)
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{
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struct processor_entry *entry;
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int need_pids;
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struct kinfo_proc *plist;
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int nproc;
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size_t size;
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processor_refill_tbl();
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long pcpu_cp_times[cplen];
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memset(pcpu_cp_times, 0, sizeof(pcpu_cp_times));
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need_pids = 0;
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TAILQ_FOREACH(entry, &processor_tbl, link) {
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if (entry->idle_pid <= 0) {
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need_pids = 1;
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continue;
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}
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assert(hr_kd != NULL);
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plist = kvm_getprocs(hr_kd, KERN_PROC_PID,
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entry->idle_pid, &nproc);
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if (plist == NULL || nproc != 1) {
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syslog(LOG_ERR, "%s: missing item with "
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"PID = %d for CPU #%d\n ", __func__,
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entry->idle_pid, entry->cpu_no);
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need_pids = 1;
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continue;
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}
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save_sample(entry, plist);
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size = cplen * sizeof(long);
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if (sysctl(cpmib, 2, pcpu_cp_times, &size, NULL, 0) == -1 &&
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!(errno == ENOMEM && size >= cplen * sizeof(long))) {
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syslog(LOG_ERR, "hrProcessorTable: sysctl(kern.cp_times) failed");
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return;
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}
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if (need_pids == 1)
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processor_get_pids();
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TAILQ_FOREACH(entry, &processor_tbl, link) {
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assert(hr_kd != NULL);
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save_sample(entry, &pcpu_cp_times[entry->cpu_no * CPUSTATES]);
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}
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proctbl_tick = this_tick;
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}
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/**
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@ -450,6 +347,36 @@ start_processor_tbl(struct lmodule *mod)
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get_cpus_samples, NULL, mod);
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}
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/**
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* Init the things for hrProcessorTable.
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* Scan the device table for processor entries.
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*/
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void
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init_processor_tbl(void)
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{
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/* create the initial processor table */
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create_proc_table();
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/* and get first samples */
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refresh_processor_tbl();
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}
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/**
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* Finalization routine for hrProcessorTable.
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* It destroys the lists and frees any allocated heap memory.
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*/
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void
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fini_processor_tbl(void)
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{
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if (cpus_load_timer != NULL) {
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timer_stop(cpus_load_timer);
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cpus_load_timer = NULL;
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}
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free_proc_table();
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}
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/**
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* Access routine for the processor table.
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*/
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@ -460,9 +387,6 @@ op_hrProcessorTable(struct snmp_context *ctx __unused,
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{
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struct processor_entry *entry;
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if (this_tick != proctbl_tick)
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refresh_processor_tbl();
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switch (curr_op) {
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case SNMP_OP_GETNEXT:
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