On Thu, Feb 08, 2018 at 05:50:16PM +0800, Wei Wang wrote: > This patch series is separated from the previous "Virtio-balloon > Enhancement" series. The new feature, VIRTIO_BALLOON_F_FREE_PAGE_HINT, > implemented by this series enables the virtio-balloon driver to report > hints of guest free pages to the host. It can be used to accelerate live > migration of VMs. Here is an introduction of this usage: > > Live migration needs to transfer the VM's memory from the source machine > to the destination round by round. For the 1st round, all the VM's memory > is transferred. From the 2nd round, only the pieces of memory that were > written by the guest (after the 1st round) are transferred. One method > that is popularly used by the hypervisor to track which part of memory is > written is to write-protect all the guest memory. > > This feature enables the optimization of the 1st round memory transfer - > the hypervisor can skip the transfer of guest free pages in the 1st round. > It is not concerned that the memory pages are used after they are given > to the hypervisor as a hint of the free pages, because they will be > tracked by the hypervisor and transferred in the next round if they are > used and written. At this point I think it's a good idea to focus on the qemu side, that code is still not really ready yet. > * Tests > - Migration time improvement > Result: > Live migration time is reduced to 14% with this optimization. > Details: > Local live migration of 8GB idle guest, the legacy live migration takes > ~1817ms. With this optimization, it takes ~254ms, which reduces the time > to 14%. > - Workload tests > Results: > Running this feature has no impact on the linux compilation workload > running inside the guest. I think you should try something memory intensive. Try asking qemu migration guys for hints on a good test to run. > Details: > Set up a Ping-Pong local live migration, where the guest ceaselessy > migrates between the source and destination. Linux compilation, > i.e. make bzImage -j4, is performed during the Ping-Pong migration. The > legacy case takes 5min14s to finish the compilation. With this > optimization patched, it takes 5min12s. How is migration time affected in this case? > ChangeLog: > v27->v28: > - mm/page_poison: Move PAGE_POISON to page_poison.c and add a function > to expose page poison val to kernel modules. > v26->v27: > - add a new patch to expose page_poisoning_enabled to kernel modules > - virtio-balloon: set poison_val to 0xaaaaaaaa, instead of 0xaa > v25->v26: virtio-balloon changes only > - remove kicking free page vq since the host now polls the vq after > initiating the reporting > - report_free_page_func: detach all the used buffers after sending > the stop cmd id. This avoids leaving the detaching burden (i.e. > overhead) to the next cmd id. Detaching here isn't considered > overhead since the stop cmd id has been sent, and host has already > moved formard. > v24->v25: > - mm: change walk_free_mem_block to return 0 (instead of true) on > completing the report, and return a non-zero value from the > callabck, which stops the reporting. > - virtio-balloon: > - use enum instead of define for VIRTIO_BALLOON_VQ_INFLATE etc. > - avoid __virtio_clear_bit when bailing out; > - a new method to avoid reporting the some cmd id to host twice > - destroy_workqueue can cancel free page work when the feature is > negotiated; > - fail probe when the free page vq size is less than 2. > v23->v24: > - change feature name VIRTIO_BALLOON_F_FREE_PAGE_VQ to > VIRTIO_BALLOON_F_FREE_PAGE_HINT > - kick when vq->num_free < half full, instead of "= half full" > - replace BUG_ON with bailing out > - check vb->balloon_wq in probe(), if null, bail out > - add a new feature bit for page poisoning > - solve the corner case that one cmd id being sent to host twice > v22->v23: > - change to kick the device when the vq is half-way full; > - open-code batch_free_page_sg into add_one_sg; > - change cmd_id from "uint32_t" to "__virtio32"; > - reserver one entry in the vq for the driver to send cmd_id, instead > of busywaiting for an available entry; > - add "stop_update" check before queue_work for prudence purpose for > now, will have a separate patch to discuss this flag check later; > - init_vqs: change to put some variables on stack to have simpler > implementation; > - add destroy_workqueue(vb->balloon_wq); > > v21->v22: > - add_one_sg: some code and comment re-arrangement > - send_cmd_id: handle a cornercase > > For previous ChangeLog, please reference > https://lwn.net/Articles/743660/ > > Wei Wang (4): > mm: support reporting free page blocks > virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT > mm/page_poison: add a function to expose page poison val to kernel > modules > virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON > > drivers/virtio/virtio_balloon.c | 258 +++++++++++++++++++++++++++++++----- > include/linux/mm.h | 8 ++ > include/linux/poison.h | 7 - > include/uapi/linux/virtio_balloon.h | 7 + > mm/page_alloc.c | 96 ++++++++++++++ > mm/page_poison.c | 24 ++++ > 6 files changed, 357 insertions(+), 43 deletions(-) > > -- > 2.7.4 -- 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>
