| commit | f8364784f00621104aa0b5b4b48e3c109b6beac5 | |
| author | David Gibson <david@gibson.dropbear.id.au> | |
| Wed, 6 Mar 2019 03:06:01 +0000 (6 14:06 +1100) | ||
| committer | Michael Roth <mdroth@linux.vnet.ibm.com> | |
| Tue, 30 Jul 2019 17:36:15 +0000 (30 12:36 -0500) | ||
| tree | 955c73b8d6d902f996af72c8e906f43ae06763f0 | treesnapshot (tar.gz zip) |
| parent | 38e8e9007d4e40840c5277e19a45f44b4314c197 | commitdiff |
virtio-balloon: Restore MADV_WILLNEED hint on balloon deflate
Prior to f6deb6d9 "virtio-balloon: Remove unnecessary MADV_WILLNEED on
deflate", the balloon device issued an madvise() MADV_WILLNEED on
pages removed from the balloon. That would hint to the host kernel
that the pages were likely to be needed by the guest in the near
future.
It's unclear if this is actually valuable or not, and so f6deb6d9
removed this, essentially ignoring balloon deflate requests. However,
concerns have been raised that this might cause a performance
regression by causing extra latency for the guest in certain
configurations.
So, until we can get actual benchmark data to see if that's the case,
this restores the old behaviour, issuing a MADV_WILLNEED when a page is
removed from the balloon.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20190306030601.21986-4-david@gibson.dropbear.id.au>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 596546fe9e4d1d1fa6423c300e2a73b6f90baeb0)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Prior to f6deb6d9 "virtio-balloon: Remove unnecessary MADV_WILLNEED on
deflate", the balloon device issued an madvise() MADV_WILLNEED on
pages removed from the balloon. That would hint to the host kernel
that the pages were likely to be needed by the guest in the near
future.
It's unclear if this is actually valuable or not, and so f6deb6d9
removed this, essentially ignoring balloon deflate requests. However,
concerns have been raised that this might cause a performance
regression by causing extra latency for the guest in certain
configurations.
So, until we can get actual benchmark data to see if that's the case,
this restores the old behaviour, issuing a MADV_WILLNEED when a page is
removed from the balloon.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20190306030601.21986-4-david@gibson.dropbear.id.au>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 596546fe9e4d1d1fa6423c300e2a73b6f90baeb0)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
| hw/virtio/virtio-balloon.c | diffblobblamehistory |