Messages in this thread | | | Date | Tue, 24 Apr 2012 09:35:31 +0900 | From | Minchan Kim <> | Subject | Re: Over-eager swapping |
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On 04/23/2012 06:27 PM, Richard Davies wrote:
> We run a number of relatively large x86-64 hosts with twenty or so qemu-kvm > virtual machines on each of them, and I'm have some trouble with over-eager > swapping on some of the machines. This is resulting in load spikes during the > swapping and customer reports of very poor response latency from the virtual > machines which have been swapped out, despite the hosts apparently having > large amounts of free memory, and running fine if swap is turned off. > > > All of the hosts are currently running a 3.1.4 or 3.2.2 kernel and have ksm > enabled with 64GB of RAM and 2x eight-core AMD Opteron 6128 processors. > However, we have seen this same problem since 2010 on a 2.6.32.7 kernel and > older hardware - see http://marc.info/?l=linux-mm&m=128075337008943 > (previous helpful contributors cc:ed here - thanks). > > We have /proc/sys/vm/swappiness set to 0. The kernel config is here: > http://users.org.uk/config-3.1.4
Although you set swappiness to 0, kernel can swap out anon pages in current implementation. I think it's a severe problem.
Couldn't this patch help you? http://permalink.gmane.org/gmane.linux.kernel.mm/74824 It can prevent anon pages's swap out until few page cache remain.
-- Kind regards, Minchan Kim
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