linux-kernel - Re: [PATCH] x86_64: Limit the number of processor bootup messages

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Date:	Fri, 30 Oct 2009 16:30:04 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Mike Travis <travis@....com>
cc:	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>,
	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>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.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 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86_64: Limit the number of processor bootup messages

On Fri, 30 Oct 2009, Mike Travis wrote:

> > > x86_64: Limit the number of processor bootup messages
> > > 

Is this really only limited to 64 bit?

> > > With a large number of processors in a system there is an excessive amount
> > > of messages sent to the system console.  It's estimated that with 4096
> > > processors in a system, and the console baudrate set to 56K, the startup
> > > messages will take about 84 minutes to clear the serial port.
> > > 
> > > This set of patches limits the number of repetitious messages which
> > > contain
> > > no additional information.  Much of this information is obtainable from
> > > the
> > > /proc and /sysfs.   Most of the messages are also sent to the kernel log
> > > buffer as KERN_DEBUG messages so it can be used to examine more closely
> > > any
> > > details specific to a processor.
> > > 
> > > The list of message transformations....
> > > 
> > > For system_state == SYSTEM_BOOTING:
> > > 
> > > 	[   25.388280] Booting Processors 1-7,320-327, Node 0
> > > 	[   26.064742] Booting Processors 8-15,328-335, Node 1
> > > 	[   26.837006] Booting Processors 16-31,336-351, Nodes 2-3
> > > 	[   28.440427] Booting Processors 32-63,352-383, Nodes 4-7
> > > 	[   31.640450] Booting Processors 64-127,384-447, Nodes 8-15
> > > 	[   38.041430] Booting Processors 128-255,448-575, Nodes 16-31
> > > 	[   50.917504] Booting Processors 256-319,576-639, Nodes 32-39
> > > 	[   90.964169] Brought up 640 CPUs
> > > 
> > > The range of processors increases as a power of 2, so 4096 CPU's should
> > > only take 12 lines.
> > > 

On your particular machine, yes, but there's no x86 restriction on the 
number of cpus per node.

> > > @@ -671,6 +759,50 @@
> > > 	complete(&c_idle->done);
> > > }
> > > 
> > > +/* Summarize the "Booting processor ..." startup messages */
> > > +static void __init print_summary_bootmsg(int cpu)
> > > +{
> > > +	static int next_node, node_shift;
> > > +	int node = cpu_to_node(cpu);
> > > +
> > > +	if (node >= next_node) {
> > > +		cpumask_var_t cpulist;
> > > +
> > > +		node = next_node;
> > > +		next_node = 1 << node_shift;
> > > +		node_shift++;
> > > +
> > > +		if (alloc_cpumask_var(&cpulist, GFP_KERNEL)) {
> > > +			int i, tmp, last_node = node;
> > > +			char buf[32];
> > > +
> > > +			cpumask_clear(cpulist);
> > > +			for_each_present_cpu(i) {
> > > +				if (i == 0)	/* boot cpu */
> > > +					continue;
> > > +
> > > +				tmp = cpu_to_node(i);
> > > +				if (node <= tmp && tmp < next_node) {
> > > +					cpumask_set_cpu(i, cpulist);
> > > +					if (last_node < tmp)
> > > +						last_node = tmp;
> > > +				}
> > > +			}
> > > +			if (cpumask_weight(cpulist)) {
> > > +				cpulist_scnprintf(buf, sizeof(buf), cpulist);
> > > +				printk(KERN_INFO "Booting Processors %s,",
> > > buf);
> > > +
> > > +				if (node == last_node)
> > > +					printk(KERN_CONT " Node %d\n", node);
> > > +				else
> > > +					printk(KERN_CONT " Nodes %d-%d\n",
> > > +						node, last_node);
> > > +			}
> > > +			free_cpumask_var(cpulist);
> > > +		}
> > > +	}
> > > +}
> > > +
> > > /*
> > >  * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
> > >  * (ie clustered apic addressing mode), this is a LOGICAL apic ID.
> > 
> > Why isn't cpumask_of_node() available yet?
> 
> I'll try that.  It gets a bit tricky in specifying the actual last node that
> is being booted.
> 

Why do you need to call print_summary_bootmsg() for each cpu?  It seems 
like you'd be able to move this out to a single call to a new function:

void __init print_summary_bootmsg(void)
{
	char buf[128];
	int nid;

	for_each_online_node(nid) {
		const struct cpumask *mask = cpumask_of_node(nid);

		if (cpumask_empty(mask))
			continue;
		cpulist_scnprintf(buf, sizeof(buf), cpumask_of_node(nid));
		pr_info("Booting Processors %s, Node %d\n", buf, nid);
	}
}
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