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| author | Stefan Hajnoczi <stefanha@redhat.com> | 2019-03-07 16:49:41 +0000 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2019-03-13 10:54:55 +0000 |
| commit | f357fcd890a8d6ced6d261338b859a41414561e9 (patch) | |
| tree | a14417ab0d8d597603bead7821548c1ef05cf586 /qapi | |
| parent | 3f3bbfc7cef4490c5ed5550766a81e7d18f08db1 (diff) | |
file-posix: add drop-cache=on|off option
Commit dd577a26ff03b6829721b1ffbbf9e7c411b72378 ("block/file-posix:
implement bdrv_co_invalidate_cache() on Linux") introduced page cache
invalidation so that cache.direct=off live migration is safe on Linux.
The invalidation takes a significant amount of time when the file is
large and present in the page cache. Normally this is not the case for
cross-host live migration but it can happen when migrating between QEMU
processes on the same host.
On same-host migration we don't need to invalidate pages for correctness
anyway, so an option to skip page cache invalidation is useful. I
investigated optimizing invalidation and detecting same-host migration,
but both are hard to achieve so a user-visible option will suffice.
As a bonus this option means that the cache invalidation feature will
now be detectable by libvirt via QMP schema introspection.
Suggested-by: Neil Skrypuch <neil@tembosocial.com>
Tested-by: Neil Skrypuch <neil@tembosocial.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20190307164941.3322-1-stefanha@redhat.com
Message-Id: <20190307164941.3322-1-stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'qapi')
| -rw-r--r-- | qapi/block-core.json | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/qapi/block-core.json b/qapi/block-core.json index 919d0530b2..ce91177bbc 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -2816,6 +2816,10 @@ # @locking: whether to enable file locking. If set to 'auto', only enable # when Open File Descriptor (OFD) locking API is available # (default: auto, since 2.10) +# @drop-cache: invalidate page cache during live migration. This prevents +# stale data on the migration destination with cache.direct=off. +# Currently only supported on Linux hosts. +# (default: on, since: 4.0) # @x-check-cache-dropped: whether to check that page cache was dropped on live # migration. May cause noticeable delays if the image # file is large, do not use in production. @@ -2828,6 +2832,8 @@ '*pr-manager': 'str', '*locking': 'OnOffAuto', '*aio': 'BlockdevAioOptions', + '*drop-cache': {'type': 'bool', + 'if': 'defined(CONFIG_LINUX)'}, '*x-check-cache-dropped': 'bool' } } ## |