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authorStefan Hajnoczi <stefanha@redhat.com>2019-03-07 16:49:41 +0000
committerStefan Hajnoczi <stefanha@redhat.com>2019-03-13 10:54:55 +0000
commitf357fcd890a8d6ced6d261338b859a41414561e9 (patch)
treea14417ab0d8d597603bead7821548c1ef05cf586 /qapi
parent3f3bbfc7cef4490c5ed5550766a81e7d18f08db1 (diff)
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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.json6
1 files changed, 6 insertions, 0 deletions
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 919d053..ce91177 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' } }
##