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

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Date:	Fri, 13 Nov 2009 10:52:49 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Travis <travis@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Roland Dreier <rdreier@...co.com>,
	Randy Dunlap <rdunlap@...otime.net>, Tejun Heo <tj@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Rientjes <rientjes@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Jack Steiner <steiner@....com>,
	Frederic Weisbecker <fweisbec@...il.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] x86: Limit the number of processor bootup messages


* Mike Travis <travis@....com> wrote:

> 
> 
> Ingo Molnar wrote:
> >* Mike Travis <travis@....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
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