On 10/08/2013 03:39 PM, Gleb Natapov wrote: > On Tue, Oct 08, 2013 at 02:58:22PM +0800, chai wen wrote: >> On 10/02/2013 12:04 AM, chaiwen wrote: >>> On 09/30/2013 08:51 PM, Gleb Natapov wrote: >>>> On Mon, Sep 30, 2013 at 06:03:07PM +0800, chai wen wrote: >>>>> Hi all >>>>> >>>>> Async page fault in kvm currently pin user pages via get_user_pages. >>>>> when doing page migration,the method can be found via >>>>> page->mmapping->a_ops->migratepage to offline old pages and migrate to >>>>> new pages. As to anonymous page there is no file mapping but a anon_vma.So >>>>> the migration will fall back to some *default* migration method.Anon pages >>>>> that have been pined in memory by some reasons could be failed in the >>>>> migration >>>>> processing because of some reasons like ref-count checking. >>>>> (or I misunderstand some thing?) >>>>> >>>>> Now we want to make these anon pages in async_pf can be migrated, I try >>>>> some >>>>> ways.But there are still many problems. The following is one that >>>>> replaceing >>>>> the mapping of anon page arbitrarily and doing some thing based on it. >>>>> Kvm-based virtual machine can works on this patch,but have no experience >>>>> of >>>>> offline pages because of the limitaion of resouces.I'll check it later. >>>>> >>>>> I don't know weather it is a right direction of this issue. >>>>> All comments/criticize are welcomed. >>>> The pinning is not mandatory and can (and probably should) be dropped, but >>>> pinning that is done by async page faults is short lived. What problems >>>> are you seeing that warrant the complexity of handling their migration? >> Hi Gleb >> >> As to this issue, I still have some thing not very clear. >> If pages pinning is successfully holding (although not mandatory) by >> async page fault. >> And at the same time page migration happens because of memory >> hot-remove action. >> It has 120*hz timeout setting in common page offline processing, >> could it fail with >> these async_pf pined pages migration ? >> What's your opinion about this ? If it may fail under this >> circumstance, should we do >> some thing on it ? >> > 120 seconds is more than enough time for pinning to go away, but as I > said the pinning is not even necessary. Patch to remove it is welcomed. Thank you for your clarification ! I've got it. we will still work on it.
> > -- > Gleb. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Regards chai wen -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
