Did that, but still problems with very high server load.
DB log shows some alarming stuff:
OS WAIT ARRAY INFO: reservation count 455
OS WAIT ARRAY INFO: signal count 377
Mutex spin waits 401, rounds 7269, OS waits 227
RW-shared spins 180, rounds 5329, OS waits 174
RW-excl spins 27, rounds 1685, OS waits 54
Spin rounds per wait: 18.13 mutex, 29.61 RW-shared, 62.41 RW-excl
------------
TRANSACTIONS
------------
Trx id counter 8728139
Purge done for trx's n:o < 8728139 undo n:o < 0 state: running but idle
History list length 982
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 8728135, not started
MySQL thread id 849, OS thread handle 0x7f68cf1b9700, query id 8809 localhost vpopmail cleaning up
---TRANSACTION 8728137, not started
MySQL thread id 848, OS thread handle 0x7f68cf401700, query id 8812 localhost vpopmail cleaning up
---TRANSACTION 8728115, not started
MySQL thread id 846, OS thread handle 0x7f68d17b6700, query id 8761 localhost vpopmail cleaning up
---TRANSACTION 8728113, not started
MySQL thread id 843, OS thread handle 0x7f68cf24b700, query id 8749 localhost vpopmail cleaning up
---TRANSACTION 8728111, not started
MySQL thread id 842, OS thread handle 0x7f68cf649700, query id 8746 localhost vpopmail cleaning up
---TRANSACTION 8728109, not started
MySQL thread id 840, OS thread handle 0x7f68d1525700, query id 8739 localhost vpopmail cleaning up
---TRANSACTION 8728107, not started
MySQL thread id 839, OS thread handle 0x7f68d17ff700, query id 8736 localhost vpopmail cleaning up
---TRANSACTION 8728105, not started
MySQL thread id 837, OS thread handle 0x7f68cf6db700, query id 8729 localhost vpopmail cleaning up
---TRANSACTION 8728128, not started
MySQL thread id 836, OS thread handle 0x7f68d15b7700, query id 8795 localhost vpopmail cleaning up
---TRANSACTION 8728103, not started
MySQL thread id 830, OS thread handle 0x7f68d1692700, query id 8726 localhost vpopmail cleaning up
---TRANSACTION 8728133, not started
MySQL thread id 829, OS thread handle 0x7f68cf56e700, query id 8807 localhost vpopmail cleaning up
---TRANSACTION 8728121, not started
MySQL thread id 827, OS thread handle 0x7f68cf525700, query id 8777 localhost vpopmail cleaning up
---TRANSACTION 8728101, not started
MySQL thread id 822, OS thread handle 0x7f68d1724700, query id 8724 localhost vpopmail cleaning up
---TRANSACTION 8728127, not started
MySQL thread id 821, OS thread handle 0x7f68cf76d700, query id 8793 localhost vpopmail cleaning up
---TRANSACTION 8728131, not started
MySQL thread id 820, OS thread handle 0x7f68d1525700, query id 8801 localhost vpopmail cleaning up
FILE I/O
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (read thread)
I/O thread 4 state: waiting for i/o request (read thread)
I/O thread 5 state: waiting for i/o request (read thread)
I/O thread 6 state: waiting for i/o request (write thread)
I/O thread 7 state: waiting for i/o request (write thread)
I/O thread 8 state: waiting for i/o request (write thread)
I/O thread 9 state: waiting for i/o request (write thread)
Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0, 0, 0, 0] ,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
7009 OS file reads, 2517 OS file writes, 557 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 2.95 writes/s, 0.90 fsyncs/s
This happens every 15-30 minutes or so.
What's going on?