linux-kernel - Re: [patch v2] x86: reduce srat verbosity in the kernel log

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Message-ID: <alpine.DEB.2.00.0910272220560.9448@chino.kir.corp.google.com>
Date:	Tue, 27 Oct 2009 22:24:39 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jack Steiner <steiner@....com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Yinghai Lu <yinghai@...nel.org>, Mel Gorman <mel@....ul.ie>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [patch v2] x86: reduce srat verbosity in the kernel log

On Wed, 28 Oct 2009, Andi Kleen wrote:

> > +		/*
> > +		 * If the bitmap cannot be listed in a buffer of length
> > +		 * APICID_LIST_LEN, then it is suffixed with "...".
> > +		 */
> > +		len = bitmap_scnlistprintf(apicid_list, APICID_LIST_LEN,
> > +					   apicid_map, MAX_LOCAL_APIC);
> > +		pr_info("SRAT: PXM %u -> APIC {%s%s} -> Node %u\n",
> > +			i, apicid_list,
> > +			(len == APICID_LIST_LEN - 1) ? "..." : "",
> 
> Is the - 1 really correct? If scnlistprintf follows snprintf semantics then it would not
> be and my understanding is it is supposed to.
> 

It is, bitmap_scnlistprintf() returns the number of characters printed to 
the buffer minus the trailing '\0', which is different from snprintf().  
APICID_LIST_LEN-1 then identifies when the buffer was max'd out.  It still 
adds a trailing "..." if the list is exactly 128 characters long, but this 
isn't addressed to avoid added complexity.
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