Messages in this thread | | | Date | Thu, 26 Apr 2012 17:08:52 +0100 | From | Richard Davies <> | Subject | Re: [RFC][PATCH] avoid swapping out with swappiness==0 |
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KOSAKI Motohiro wrote: > Christoph Lameter wrote: > > Richard Davies wrote: > > > > > I strongly believe that Linux should have a way to turn off swapping unless > > > absolutely necessary. This means that users like us can run with swap > > > present for emergency use, rather than having to disable it because of the > > > side effects. > > > > Agree. And this ooperation mode should be the default behavior given that > > swapping is a very slow and tedious process these days. > > Even though current patch is not optimal, I don't disagree this opinion. Can > you please explain your use case? Why don't you use swapoff?
My use case is that I have large (64 or 128GB RAM) qemu-kvm virtualization hosts, running many (20-50) VMs.
Typically the total memory in use is less than physical memory. In these cases I would like the virtualization host to run without any swapping. I have set swappiness==0, but in practise I get big load spikes from swapping. See http://marc.info/?l=linux-mm&m=133517452117581
I don't want to run swapoff, because sometimes I will need to provision slightly more VMs than physical memory, and in these cases I would rather that the system runs with a little swap in use rather than the OOM killer occurring.
Richard.
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