On Tue, Apr 19, 2016 at 03:02:09PM +0000, Li, Liang Z wrote: > > On Tue, 2016-04-19 at 22:34 +0800, Liang Li wrote: > > > The free page bitmap will be sent to QEMU through virtio interface and > > > used for live migration optimization. > > > Drop the cache before building the free page bitmap can get more free > > > pages. Whether dropping the cache is decided by user. > > > > > > > How do you prevent the guest from using those recently-freed pages for > > something else, between when you build the bitmap and the live migration > > completes? > > Because the dirty page logging is enabled before building the bitmap, there is no need > to prevent the guest from using the recently-freed pages ... > > Liang Well one point of telling host that page is free is so that it can mark it clean even if it was dirty previously. So I think you must pass the pages to guest under the lock. This will allow host optimizations such as marking these pages MADV_DONTNEED or MADV_FREE. Otherwise it's all too tied up to a specific usecase - you aren't telling host that a page is free, you are telling it that a page was free in the past. -- MST -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>