This series provides an asynchronous means of reporting free guest pages
to QEMU through virtio-balloon so that the memory associated with those
pages can be dropped and reused by other processes and/or guests on the
host. Using this it is possible to avoid unnecessary I/O to disk and
greatly improve performance in the case of memory overcommit on the host.
I originally submitted this patch series back on February 11th 2020[1],
but at that time I was focused primarily on the kernel portion of this
patch set. However as of April 7th those patches are now included in
Linus's kernel tree[2] and so I am submitting the QEMU pieces for
inclusion.
[1]: https://lore.kernel.org/lkml/20200211224416.29318.44077.stgit@localhost.localdomain/
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b0c504f154718904ae49349147e3b7e6ae91ffdc
Changes from v17:
Fixed typo in patch 1 title
Addressed white-space issues reported via checkpatch
Added braces {} for two if statements to match expected coding style
Changes from v18:
Updated patches 2 and 3 based on input from dhildenb
Added comment to patch 2 describing what keeps us from reporting a bad page
Added patch to address issue with ROM devices being directly writable
Changes from v19:
Added std-headers change to match changes pushed for linux kernel headers
Added patch to remove "report" from page hinting code paths
Updated comment to better explain why we disable hints w/ page poisoning
Removed code that was modifying config size for poison vs hinting
Dropped x-page-poison property
Added code to bounds check the reported region vs the RAM block
Dropped patch for ROM devices as that was already pulled in by Paolo
Changes from v20:
Rearranged patches to push Linux header sync patches to front
Removed association between free page hinting and VIRTIO_BALLOON_F_PAGE_POISON
Added code to enable VIRTIO_BALLOON_F_PAGE_POISON if page reporting is enabled
Fixed possible resource leak if poison or qemu_balloon_is_inhibited return true
Changes from v21:
Added ack for patch 3
Rewrote patch description for page poison reporting feature
Made page-poison independent property and set to enabled by default
Added logic to migrate poison_val
Added several comments in code to better explain features
Switched free-page-reporting property to disabled by default
Changes from v22:
Added ack for patches 4 & 5
Added additional comment fixes in patch 3 to remove "reporting" reference
Renamed rvq in patch 5 to reporting_vq to better match linux kernel
Moved call adding reporting_vq to after free_page_vq
Changes from v23:
Rebased on latest QEMU
Dropped patches 1 & 2 as Linux kernel headers were synced
Added compat machine bits for page-poison feature
---
Alexander Duyck (3):
virtio-balloon: Replace free page hinting references to 'report' with 'hint'
virtio-balloon: Implement support for page poison reporting feature
virtio-balloon: Provide an interface for free page reporting
hw/core/machine.c | 4 +
hw/virtio/virtio-balloon.c | 176 ++++++++++++++++++++++++++++--------
include/hw/virtio/virtio-balloon.h | 23 ++---
3 files changed, 152 insertions(+), 51 deletions(-)
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