Modify the design of token bucket to save more tokens than burst value,
so as to support continuous burst. The desired burst duration can be
controlled by rbd_qos_XYZ_burst_seconds.
Fixes: https://tracker.ceph.com/issues/45313
Signed-off-by: wencong wan <wanwc@chinatelecom.cn>
When a snapshot-based image is non-primary, we will need to use
this implicit feature to ensure that writes and maintenance
operations cannot be performed against the image.
Signed-off-by: Jason Dillaman <dillaman@redhat.com>
Clean up the caching sections to match the current implementation and
clarify which sections apply only to librbd.
Signed-off-by: Jason Dillaman <dillaman@redhat.com>
Older guests may not send flushes properly (i.e. never), so if this is
enabled, rbd_cache=true is safe for them transparently.
Disable by default, since it will unnecessarily slow down newer guest
boot, and prevent writeback caching for things that don't need to send
flushes, like the command line tool.
Refs: #3817
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
