VM Problems in 2.6.7 (Too active OOM Killer)

From: Peter Zaitsev
Date: Tue Jul 13 2004 - 21:26:16 EST


Hi,

To be honest I was truly surprised seeing OOM killer killing MySQL
without any good reason during highly IO intensive test:

Out of Memory: Killed process 19301 (mysqld).
Out of Memory: Killed process 19302 (mysqld).
Out of Memory: Killed process 19303 (mysqld).
Out of Memory: Killed process 19304 (mysqld).
Out of Memory: Killed process 19305 (mysqld).
Out of Memory: Killed process 19306 (mysqld).
Out of Memory: Killed process 19309 (mysqld).
Out of Memory: Killed process 19310 (mysqld).
Out of Memory: Killed process 19311 (mysqld).
Out of Memory: Killed process 19312 (mysqld).
Out of Memory: Killed process 19737 (mysqld).
Out of Memory: Killed process 19739 (mysqld).
Out of Memory: Killed process 19821 (mysqld).


This box has 4G memory and running without swap (what I would need it
for If I can only use up to 3GB address space in the application anyway)


Here is how VMSTAT Looked like:

0 4 0 7028 43436 1656020 0 0 3988 8752 1716 11803 8
5 45 43
0 9 0 7004 42520 1654692 0 0 4372 8642 1735 12803 8
5 41 46
2 3 0 7828 40784 1654252 0 0 4024 7838 1662 11486 7
4 44 45
5 13 0 7228 38652 1653800 0 0 4370 9087 1751 12864 9
5 40 47
0 2 0 5928 32976 1645808 0 0 4954 8866 1890 13352 9
5 39 47
0 15 0 6560 22052 1642996 0 0 5111 7699 2004 11819 8
5 41 47
0 2 0 6232 15760 1642624 0 0 4630 6841 1912 10315 6
4 46 45
1 6 0 7804 10912 1640332 0 0 4493 6446 1913 9362 6
4 48 43
0 5 0 391660 6080 1267356 0 0 4265 6404 1902 9483 6
4 46 44
procs memory swap io
system cpu
r b swpd free buff cache si so bi bo in cs us sy
id wa
0 2 0 330392 5696 1319216 0 0 4674 6309 1949 9792 6
4 46 44
0 2 0 278052 3520 1363212 0 0 4155 5177 1827 7459 4
6 48 42
1 0 0 2188840 5676 1387984 0 0 2176 2104 1410 21275 5
33 41 21
0 1 0 2121864 16948 1421456 0 0 1110 3600 1317 85261 11
23 58 8
1 0 0 2062688 27072 1454988 0 0 997 3612 1302 84842 11
22 58 9
0 1 0 1997464 38160 1488236 0 0 1096 3685 1319 85041 11
23 59 8
0 1 0 1930536 52184 1521540 0 0 1391 4318 1476 84995 11
23 58 9
0 1 0 1841888 69896 1555032 0 0 1758 3630 1478 84814 11
23 58 8
0 1 0 1758272 85860 1588504 0 0 1597 3651 1460 84212 11
23 58 8
0 1 0 1683696 101220 1621764 0 0 1524 3694 1432 84605 11
23 58 8
0 1 0 1609016 115756 1655032 0 0 1440 3802 1400 84774 11
23 59 8


So we had some 1.4GB of memory in "cached" state, so why not to shrink
cache instead ?

I hope we're not going back to 2.4 times, where a lot of people fought
with VM/OOM problems and lost :)


I now this is likely not that much helpful and a lot more info is
needed. I'll see if I run into this again and will be asking which
information exactly is needed to troubleshoot the problem.





--
Peter Zaitsev, Senior Support Engineer
MySQL AB, www.mysql.com



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