linux-kernel - Re: [PATCH 3/4] RAS: Add a Corrected Errors Collector

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Date:   Thu, 23 Mar 2017 16:22:28 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     X86 ML <x86@...nel.org>, linux-edac <linux-edac@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] RAS: Add a Corrected Errors Collector

On Wed, Mar 22, 2017 at 07:03:39PM +0100, Borislav Petkov wrote:
> Lemme try to write a small script exercising exactly that scenario to
> see whether I'm actually not talking crap here :-)

Ok, here's a snapshot from the CEC after letting it run for a couple of
hours in a guest with a script running twice in parallel and injecting
random PFNs. We have 0 offlined pages because a PFN number doesn't
repeat frequently enough to cause an overflow.

When I force the occurrence of a single PFN for 1023 and more times and
do that more than once, this happens:

[ 6629.091239] RAS: Soft-offlining pfn: 0x7fff
[ 6629.093036] __get_any_page: 0x7fff free buddy page
[ 6653.259476] RAS: Soft-offlining pfn: 0x7fff
[ 6653.260100] soft offline: 0x7fff page already poisoned

...

Stats:
CEs: 32614
offlined pages: 2
^^^^^^^^^^^^^^^^^

Flags: 0x0
Timer interval: 86400 seconds
Decays: 254
Action threshold: 1023

The "already poisoned" thing shouldn't happen in real life because once
the page frame is poisoned, it shouldn't generate MCEs.




Every 2.0s: head -n 40 array; tail -n 40 array                                                   Thu Mar 23 17:15:15 2017

{ n: 512
 000: [0000000000000056|c01]
 001: [000000000000011f|801]
 002: [0000000000000171|401]
 003: [00000000000001ce|401]
 004: [000000000000024a|401]
 005: [000000000000026e|401]
 006: [000000000000034d|c01]
 007: [0000000000000395|c01]
 008: [00000000000003b9|801]
 009: [0000000000000458|003]
 010: [000000000000045c|401]
 011: [00000000000004f9|401]
 012: [00000000000005d1|c01]
 013: [0000000000000677|801]
 014: [000000000000069d|401]
 015: [00000000000006b3|401]
 016: [00000000000006f5|c01]
 017: [00000000000006fc|401]
 018: [000000000000074d|401]
 019: [0000000000000764|c01]
 020: [00000000000008a8|801]
 021: [0000000000000951|401]
 022: [0000000000000994|401]
 023: [0000000000000aa8|401]
 024: [0000000000000ac7|801]
 025: [0000000000000af2|801]
 026: [0000000000000bb5|801]
 027: [0000000000000bd5|401]
 028: [0000000000000be0|c01]
 029: [0000000000000c30|c01]
 030: [0000000000000c61|801]
 031: [0000000000000c8a|401]
 032: [0000000000000d0d|801]
 033: [0000000000000d2a|003]
 034: [0000000000000d4d|401]
 035: [0000000000000d87|c01]
 036: [0000000000000da4|c01]
 037: [0000000000000e06|401]
 038: [0000000000000e23|c01]

 ...

 480: [0000000000007d22|005]
 481: [0000000000007d5f|002]
 482: [0000000000007d9f|004]
 483: [0000000000007db1|c01]
 484: [0000000000007dbf|002]
 485: [0000000000007dcf|002]
 486: [0000000000007dd8|401]
 487: [0000000000007df0|001]
 488: [0000000000007df4|002]
 489: [0000000000007e1f|003]
 490: [0000000000007e35|801]
 491: [0000000000007e73|003]
 492: [0000000000007e77|401]
 493: [0000000000007e80|002]
 494: [0000000000007e9c|002]
 495: [0000000000007eac|002]
 496: [0000000000007ecb|002]
 497: [0000000000007ed8|801]
 498: [0000000000007edc|003]
 499: [0000000000007ee3|801]
 500: [0000000000007f05|004]
 501: [0000000000007f15|002]
 502: [0000000000007f51|004]
 503: [0000000000007f5e|003]
 504: [0000000000007f80|801]
 505: [0000000000007f92|003]
 506: [0000000000007fb2|002]
 507: [0000000000007fd9|002]
 508: [0000000000007fdf|002]
 509: [0000000000007fe5|004]
 510: [0000000000007ff4|801]
 511: [0000000000007ffa|001]
}
Stats:
CEs: 30074
offlined pages: 0
Flags: 0x0
Timer interval: 86400 seconds
Decays: 234
Action threshold: 1023

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.