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

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Date:	Tue, 10 Nov 2009 22:57:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	David Rientjes <rientjes@...gle.com>, 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,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, Andi Kleen <andi@...stfloor.org>
Subject: Re: [patch v2] x86: reduce srat verbosity in the kernel log


* Yinghai Lu <yinghai@...nel.org> wrote:

> Ingo Molnar wrote:
> > * David Rientjes <rientjes@...gle.com> wrote:
> > 
> >> On Tue, 27 Oct 2009, David Rientjes wrote:
> >>
> >>> x86: reduce srat verbosity in the kernel log
> >>>
> >>> It's possible to reduce the number of SRAT messages emitted to the kernel
> >>> log by printing each valid pxm once and then creating bitmaps to represent
> >>> the apic ids that map to the same node.
> >>>
> >>> This reduces lines such as
> >>>
> >>> 	SRAT: PXM 0 -> APIC 0 -> Node 0
> >>> 	SRAT: PXM 0 -> APIC 1 -> Node 0
> >>> 	SRAT: PXM 1 -> APIC 2 -> Node 1
> >>> 	SRAT: PXM 1 -> APIC 3 -> Node 1
> >>>
> >>> to
> >>>
> >>> 	SRAT: PXM 0 -> APIC {0-1} -> Node 0
> >>> 	SRAT: PXM 1 -> APIC {2-3} -> Node 1
> >>>
> >>> The buffer used to store the apic id list is 128 characters in length.
> >>> If that is too small to represent all the apic id ranges that are bound
> >>> to a single pxm, a trailing "..." is added.  APICID_LIST_LEN should be
> >>> manually increased for such configurations.
> >>>
> >>> Acked-by: Mike Travis <travis@....com>
> >>> Signed-off-by: David Rientjes <rientjes@...gle.com>
> >> Ingo, have you had a chance to look at merging this yet?
> > 
> > I'm waiting for Mike to test them (and other patches) and send a new 
> > series out with bits to pick up.
> > 
> > But i really dont like such type of buffering - in the past they tended 
> > to be problematic. Why print this info at all in the default bootup?  
> > It's not needed on a correctly functioning system.
> > 
> > For failure analysis make it opt-in available via a boot parameter (if 
> > it's needed for bootup analysis) - but otherwise just dont print it.
> > 
> make them to depend on apic=debug or apic=verbose?

Yeah - i'd definitely suggest to not splinter the boot flag space too 
much - users wont know what to enable in case of trouble.

But that is a detail (and it can be improved later on as well).

	Ingo
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