linux-kernel - Re: [RFC] amd64_edac: syndromes loading

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Message-ID: <797900.98239.qm@web50101.mail.re2.yahoo.com>
Date:	Thu, 5 Nov 2009 13:15:28 -0800 (PST)
From:	Doug Thompson <norsk5@...oo.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Borislav Petkov <borislav.petkov@....com>
Cc:	Pavel Machek <pavel@....cz>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, x86 <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] amd64_edac: syndromes loading



--- On Thu, 11/5/09, Borislav Petkov <borislav.petkov@....com> wrote:

> From: Borislav Petkov <borislav.petkov@....com>
> Subject: Re: [RFC] amd64_edac: syndromes loading
> To: "H. Peter Anvin" <hpa@...or.com>
> Cc: "Pavel Machek" <pavel@....cz>, "Doug Thompson" <norsk5@...oo.com>, "Ingo Molnar" <mingo@...e.hu>, "Thomas Gleixner" <tglx@...utronix.de>, "x86" <x86@...nel.org>, "LKML" <linux-kernel@...r.kernel.org>
> Date: Thursday, November 5, 2009, 6:27 AM
> Hi,
> 
> The good news is they've come up with a modified algorithm
> which will
> require a smaller table, roughly 1/4th the size of the
> current 10K one.
> Now, on a second thought and IMHO, we should simply add
> another .c file
> instantiating those two x4 and x8 tables statically and
> linking them
> into the edac code. This way you
> 
> 1) don't have the additional complexity of adding firmware
> handling code
> and thus don't add a dependency on the firmware API
> 
> 2) don't have to actually carry two firmware images with
> the kernel
> 
> See, the natural use case for those tables are big machines
> which do not
> care about 4K memory wasted in ECC decoding tables when the
> recovery
> from the missed early warnings of a failing DIMM module is
> much more
> expensive.

very well put.  when nodes that have 64 or 128 GIGA-bytes of RAM are involved, 4k or even 32kb "loss" is in the noise.

Features vs costs is always something to weigh. In some cases loss of 4k in a 1 Gb machine might not be tolerated (though I accept it).

doug t

> 
> Hmm... ?
> 
> -- 
> Regards/Gruss,
> Boris.
> 
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