kswapd in D state does slow down the whole system

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Environment

SUSE Linux Enterprise Server 10 Service Pack 3

Situation

kswapd is hogging the CPU by parking itself on state 2 (TASK_UNINTERRUPTIBLE).
This does also happen when swap is turned off. Furthermore, there is a high IO activity, whereas just a small amount of RAM is being used.

A generated crashdump does show the following backtrace:

crash> bt ffff810323e607d0

PID: 198    TASK: ffff810323e607d0  CPU: 1   COMMAND: "kswapd0"

 #0 [ffff810323e81c88] schedule at ffffffff802f010b

 #1 [ffff810323e81d60] schedule_timeout at ffffffff802f0cac

 #2 [ffff810323e81db0] io_schedule_timeout at ffffffff802f04d4

 #3 [ffff810323e81de0] blk_congestion_wait at ffffffff801f1e5c

 #4 [ffff810323e81e30] balance_pgdat at ffffffff8016c2b8

 #5 [ffff810323e81ee0] kswapd at ffffffff8016cbe6

 #6 [ffff810323e81f50] kernel_thread at ffffffff8010bec6

Resolution

It appears that the issue is due to the lack of large memory chunk. As consequence of this, a high order allocation (like 10) does fail.

This bug has been fixed and released with kernel version 2.6.16.60-0.74.7.
To fix this issue, update the kernel to the above release or a posterior one.

Additional Information

Disclaimer

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