Hello Christoph!
On Sat, 2 Dec 2006, Christoph Anton Mitterer wrote:
I found a severe bug mainly by fortune because it occurs very rarely.
My test looks like the following: I have about 30GB of testing data on
This sounds very familiar! One of the Linux compute clusters I
administer at work is a 336 node system consisting of the
following components:
* 2x Dual-Core AMD Opteron 275
* Tyan S2891 mainboard
* Hitachi HDS728080PLA380 harddisk
* 4 GB RAM (some nodes have 8 GB) - intensively tested with
memtest86+
* SUSE 9.3 x86_64 (kernel 2.6.11.4-21.14-smp) - But I've also
e.g. tried the latest openSUSE 10.2 RC1+ kernel 2.6.18.2-33 which
makes no difference.
We are running LS-Dyna on these machines and discovered a
testcase which shows a similar data corruption. So I can
confirm that the problem is for real an not a hardware defect
of a single machine!
Here's a diff of a corrupted and a good file written during our
testcase:
("-" == corrupted file, "+" == good file)
...
009f2ff0 67 2a 4c c4 6d 9d 34 44 ad e6 3c 45 05 9a 4d c4 |g*L.m.4D..<E..M.|
-009f3000 39 60 e6 44 20 ab 46 44 56 aa 46 44 c2 35 e6 44 |9.D .FDV.FD.5.D|
-009f3010 45 e1 48 44 88 3d 47 44 f3 81 e6 44 93 0b 46 44 |E.HD.=GD...D..FD|
-009f3020 d4 eb 48 44 22 57 e6 44 3d 3d 48 44 ac 89 49 44 |..HD"W.D==HD..ID|
-009f3030 00 8c e9 44 39 af 2d 44 e7 1b 8d 44 a8 6e e9 44 |...D9.-D...D.n.D|
-009f3040 16 d4 2e 44 5e 12 8c 44 78 51 e9 44 c0 f5 2f 44 |...D^..DxQ.D../D|
...
-009f3fd0 22 ae 4e 44 81 b5 ee 43 0c 8a df 44 8d e2 6b 44 |".ND...C...D..kD|
-009f3fe0 6c a0 e8 43 b6 8f e9 44 22 ae 4e 44 55 e9 ed 43 |l..C...D".NDU..C|
-009f3ff0 a8 b2 e0 44 78 7c 69 44 56 6f e8 43 5e b2 e0 44 |...Dx|iDVo.C^..D|
+009f3000 1b 32 30 44 50 59 3d 45 a2 79 4e c4 66 6e 2f 44 |.20DPY=E.yN.fn/D|
+009f3010 40 91 3d 45 d1 b6 4e c4 a1 6c 31 44 1b cb 3d 45 |@.=E..N..l1D..=E|
+009f3020 0d f6 4e c4 57 7c 33 44 bf cb 3c 45 88 9a 4d c4 |..N.W|3D..<E..M.|
+009f3030 79 e9 29 44 3a 10 3d 45 d3 e1 4d c4 17 28 2c 44 |y.)D:.=E..M..(,D|
+009f3040 f6 50 3d 45 dc 25 4e c4 b6 50 2e 44 b3 4f 3c 45 |.P=E.%N..P.D.O<E|
...
+009f3fd0 9c 70 6c 45 04 be 9f c3 fe fc 8f 44 ce 65 6c 45 |.plE.......D.elE|
+009f3fe0 fc 56 9c c3 32 f7 90 44 e5 3c 6c 45 cd 79 9c c3 |.V..2..D.<lE.y..|
+009f3ff0 f3 55 92 44 c1 10 6c 45 5e 12 a0 c3 60 31 93 44 |.U.D..lE^...1.D|
009f4000 88 cd 6b 45 c1 6d cd c3 00 a5 8b 44 f2 ac 6b 45 |..kE.m.....D..kE|
...
Please notice:
a) the corruption begins at a page boundary
b) the corrupted byte range is a single memory page and
c) almost every fourth byte is set to 0x44 in the corrupted case
(but the other bytes changed, too)
To me this looks as if a wrong memory page got written into the
file.
From our testing I can also tell that the data corruption does
*not* appear at all when we are booting the nodes with mem=2G.
However, when we are using all the 4GB the data corruption
shows up - but not everytime and thus not on all nodes.
Sometimes a node runs for ours without any problem. That's why
we are testing on 32 nodes in parallel most of the time. I have
the impression that it has something to do with physical memory
layout of the running processes.
Please also notice that this is a silent data corruption. I.e.
there are no error or warning messages in the kernel log or the
mce log at all.
Christoph, I will carefully re-read your entire posting and the
included links on Monday and will also try the memory hole
setting.
If somebody has an explanation for this problem I can offer
some of our compute nodes+time for testing because we really
want to get this fixed as soon as possible.
Best regards,
Karsten
--
Dipl.-Inf. Karsten Weiss - http://www.machineroom.de/knweiss
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