linux-kernel - Re: [PATCH 5/7 v6] trace, RAS: Add eMCA trace event interface

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Date:	Fri, 30 May 2014 12:07:16 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Chen, Gong" <gong.chen@...ux.intel.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, tony.luck@...el.com,
	m.chehab@...sung.com, linux-acpi@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/7 v6] trace, RAS: Add eMCA trace event interface

On Fri, May 30, 2014 at 05:22:32AM -0400, Chen, Gong wrote:
> We have two big chunk string. One for memory error location, the other
> for DIMM error location. Since DIMM error location depends on some
> other conditions, how about just converting memory error location to a
> compact mode but leaving DIMM error location alone?

Please elaborate, what conditions? DIMM silk screen labels or so? Maybe
we can generate a mapping between text labels and indices and we can
dump the indices in the tracepoint and do the mapping back to strings in
userspace...?

> For memory error location, I will utilize type offset to save one
> more byte, furthermore, I want to drop requestor_id, responder_id
> and target_id. 1) They are very rare (I've never seen them by now)

My concern is, are we sure we're never going to need them at all? Tony,
what's your take on this?

> 2) They are u64 but not u16. So to keep whole struct clean I want
> to use following struct. We can extend it later when necessary.
> 
> struct __attribute__((__packed__)) cper_sec_mem_rec {
> 	u8 type;
> 	u16 data;
> };
> 
> So whole struct is just 3 bytes. Even if all fields are valid, we
> have 3 * 9 = 27 bytes in total for a record in the ring buffer.
> 
> Make sense?

That is definitely much better than what we have now.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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