Messages in this thread | | | Date | Fri, 30 Apr 2010 10:13:40 +0300 | From | Avi Kivity <> | Subject | Re: Frontswap [PATCH 0/4] (was Transcendent Memory): overview |
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On 04/30/2010 04:45 AM, Dave Hansen wrote: > > A large portion of CMM2's gain came from the fact that you could take > memory away from guests without _them_ doing any work. If the system is > experiencing a load spike, you increase load even more by making the > guests swap. If you can just take some of their memory away, you can > smooth that spike out. CMM2 and frontswap do that. The guests > explicitly give up page contents that the hypervisor does not have to > first consult with the guest before discarding. >
Frontswap does not do this. Once a page has been frontswapped, the host is committed to retaining it until the guest releases it. It's really not very different from a synchronous swap device.
I think cleancache allows the hypervisor to drop pages without the guest's immediate knowledge, but I'm not sure.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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