Messages in this thread | | | Date | Thu, 16 Mar 2006 17:23:01 -0500 (EST) | From | Rik van Riel <> | Subject | Re: OOM kiler/load problems with RAID/LVM and AoE |
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On Mon, 13 Mar 2006, Joshua Kugler wrote:
> RAID or LVM problem? AoE drivers? Network driver badness (for both of them)?
You could simply be hitting a fundamental problem that's present on most operating systems. It happens roughly like this:
1) free memory gets low, so kswapd starts evicting pages 2) in order to write pages out over the network, the kernel needs to allocate memory to compose network packets, headers, etc... 3) if kswapd writes out a bunch of pages at once, or simply if memory was low to begin with when we hit (1), there may not be enough free memory left to receive the ACK packets from the NAS box that acknowledge that the data was received, nor the packets that indicate that the data was written to disk and the kernel can complete the IO
Locally attached disks do not have this problem because the kernel keeps a number of reserved buffer heads around to get us out of this deadlock problem.
Networking will need something similar. Because this is slowly turning into an FAQ, I've written down the problem and a proposed solution:
http://linux-mm.org/NetworkStorageDeadlock
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