Messages in this thread | | | Date | Wed, 10 Apr 2013 00:32:31 -0400 | From | "Michael R. Hines" <> | Subject | Re: [PATCHv2] rdma: add a new IB_ACCESS_GIFT flag |
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On 04/09/2013 11:24 PM, Michael S. Tsirkin wrote: > Which mechanism do you refer to? You patches still seem to pin each > page in guest memory at some point, which will break all COW. In > particular any pagemap tricks to detect duplicates on source that I > suggested won't work.
Sorry, I mispoke. I'm reffering to dynamic server page registration.
Of course it does not eliminate pinning - but it does mitigate the foot print of the VM as a feature that was requested.
I have implemented it and documented it.
- Michael
>> On 04/09/2013 03:03 PM, Michael S. Tsirkin wrote: >>> presumably is_dup_page reads the page, so should not break COW ... >>> >>> I'm not sure about the cgroups swap limit - you might have >>> too many non COW pages so attempting to fault them all in >>> makes you exceed the limit. You really should look at >>> what is going on in the pagemap, to see if there's >>> measureable gain from the patch. >>> >>> >>> On Fri, Apr 05, 2013 at 05:32:30PM -0400, Michael R. Hines wrote: >>>> Well, I have the "is_dup_page()" commented out.......when RDMA is >>>> activated..... >>>> >>>> Is there something else in QEMU that could be touching the page that >>>> I don't know about? >>>> >>>> - Michael >>>> >>>> >>>> On 04/05/2013 05:03 PM, Roland Dreier wrote: >>>>> On Fri, Apr 5, 2013 at 1:51 PM, Michael R. Hines >>>>> <mrhines@linux.vnet.ibm.com> wrote: >>>>>> Sorry, I was wrong. ignore the comments about cgroups. That's still broken. >>>>>> (i.e. trying to register RDMA memory while using a cgroup swap limit cause >>>>>> the process get killed). >>>>>> >>>>>> But the GIFT flag patch works (my understanding is that GIFT flag allows the >>>>>> adapter to transmit stale memory information, it does not have anything to >>>>>> do with cgroups specifically). >>>>> The point of the GIFT patch is to avoid triggering copy-on-write so >>>>> that memory doesn't blow up during migration. If that doesn't work >>>>> then there's no point to the patch. >>>>> >>>>> - R. >>>>>
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