Re: [PATCH 1/7] x86: Limit the number of processor bootup messages

Mike Travis
2009-11-13T13:43:17Z

Ingo Molnar wrote:
> * Mike Travis <travis@sgi.com> wrote:
>
>>
>> Ingo Molnar wrote:
>>> * Mike Travis <travis@sgi.com> wrote:
>>>
>>>> --- linux.orig/arch/x86/kernel/smpboot.c
>>>> +++ linux/arch/x86/kernel/smpboot.c
>>>> @@ -442,6 +442,84 @@
>>>> return c->llc_shared_map;
>>>> }
>>>> +/* Summarize Processor Information */
>>>> +static void __init summarize_cpu_info(void)
>>>> +{
>>>> + cpumask_var_t cpulist, cpusdone;
>>>> + int cpu;
>>>> + int err = 0;
>>>> +
>>>> + if (!alloc_cpumask_var(&cpulist, GFP_KERNEL))
>>>> + err = 1;
>>>> + else if (!alloc_cpumask_var(&cpusdone, GFP_KERNEL)) {
>>>> + free_cpumask_var(cpulist);
>>>> + err = 1;
>>>> + }
>>>> + if (err) {
>>>> + printk(KERN_INFO "Can't print processor summaries\n");
>>>> + return;
>>>> + }
>>>> +
>>>> + cpumask_clear(cpusdone);
>>>> + for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
>>>> + struct cpuinfo_x86 *c;
>>>> + char buf[128];
>>>> + int ncpu, len;
>>>> + unsigned long minlpj, maxlpj, avglpj = 0;
>>>> +
>>>> + /* skip if cpu has already been displayed */
>>>> + if (cpumask_test_cpu(cpu, cpusdone))
>>>> + continue;
>>>> +
>>>> + c = &cpu_data(cpu);
>>>> + minlpj = ULONG_MAX;
>>>> + maxlpj = 0;
>>>> +
>>>> + cpumask_clear(cpulist);
>>>> +
>>>> + /* collate all cpus with same specifics */
>>>> + for (ncpu = cpu; ncpu < nr_cpu_ids; ncpu++) {
>>>> + struct cpuinfo_x86 *n = &cpu_data(ncpu);
>>>> +
>>>> + if (c->x86 != n->x86 ||
>>>> + c->x86_vendor != n->x86_vendor ||
>>>> + c->x86_model != n->x86_model ||
>>>> + c->x86_mask != n->x86_mask ||
>>>> + strcmp(c->x86_model_id, n->x86_model_id))
>>>> + continue;
>>>> +
>>>> + cpumask_set_cpu(ncpu, cpulist);
>>>> + cpumask_set_cpu(ncpu, cpusdone);
>>>> +
>>>> + if (cpu_data(ncpu).loops_per_jiffy < minlpj)
>>>> + minlpj = cpu_data(ncpu).loops_per_jiffy;
>>>> +
>>>> + if (cpu_data(ncpu).loops_per_jiffy > maxlpj)
>>>> + maxlpj = cpu_data(ncpu).loops_per_jiffy;
>>>> +
>>>> + avglpj += cpu_data(ncpu).loops_per_jiffy;
>>>> + }
>>>> +
>>>> + len = cpulist_scnprintf(buf, sizeof(buf), cpulist);
>>>> + printk(KERN_INFO
>>>> + "Processor Information for CPUS: %s%s\n",
>>>> + buf, (len == sizeof(buf)-1) ? "..." : "");
>>>> +
>>>> + printk(KERN_INFO);
>>>> + print_cpu_info(c);
>>>> +
>>>> + avglpj /= cpumask_weight(cpulist);
>>>> + printk(KERN_INFO "BogoMIPS: MIN %lu.%02lu (%lu) "
>>>> + "AVG %lu.%02lu (%lu) MAX %lu.%02lu (%lu)\n",
>>>> + minlpj/(500000/HZ), (minlpj/(5000/HZ)) % 100, minlpj,
>>>> + avglpj/(500000/HZ), (avglpj/(5000/HZ)) % 100, avglpj,
>>>> + maxlpj/(500000/HZ), (maxlpj/(5000/HZ)) % 100, maxlpj);
>>>> + }
>>>> +
>>>> + free_cpumask_var(cpusdone);
>>>> + free_cpumask_var(cpulist);
>>>> +}
>>>> +
>>> Sigh, that's _way_ too complex.
>>>
>>> If you cannot print it in a summarized way without carrying over
>>> stupid state like bitmaps then please do the simple and obvious,
>>> and print:
>>>
>>> booting CPUs: #0 #1 #2 #3 #4 #5 #6 ...
>> That is almost exactly what it does. [...]
>
> You are missing my point i think, which is that we dont want the 76
> lines long summarize_cpu_info() complexity during bootup. Lets keep it
> _very_ simple and zap excessive messages - like DaveJ's patch did.
>
> Ingo

Ok, I'll zap the summary as I'm not sure how much easier to make a function
that scans the cpus to find ones that are common, and print their specific
information. If I can include the model id and stepping in some /proc
interface, then a user app could do the same thing (though I'm not sure if
BogoMIPs is available or not.)

Btw, I don't actually see the difference between the two functions, both
scan a bit map list (apics vs. cpus) to find unprocessed items, then
collates similar items comparing (nodeid vs. cpu specifics) and then
prints a summary using the scnlistprintf to gather progressive item #'s.
But maybe I'm missing something.

Thanks,
Mike