mirror of
https://github.com/ceph/ceph
synced 2024-12-18 09:25:49 +00:00
29 lines
1.2 KiB
ReStructuredText
29 lines
1.2 KiB
ReStructuredText
==================
|
|
Writeback Throttle
|
|
==================
|
|
|
|
Previously, the filestore had a problem when handling large numbers of
|
|
small ios. We throttle dirty data implicitly via the journal, but
|
|
a large number of inodes can be dirtied without filling the journal
|
|
resulting in a very long sync time when the sync finally does happen.
|
|
The flusher was not an adequate solution to this problem since it
|
|
forced writeback of small writes too eagerly killing performance.
|
|
|
|
WBThrottle tracks unflushed io per hobject_t and ::fsyncs in lru
|
|
order once the start_flusher threshold is exceeded for any of
|
|
dirty bytes, dirty ios, or dirty inodes. While any of these exceed
|
|
the hard_limit, we block on throttle() in _do_op.
|
|
|
|
See src/os/WBThrottle.h, src/osd/WBThrottle.cc
|
|
|
|
To track the open FDs through the writeback process, there is now an
|
|
fdcache to cache open fds. lfn_open now returns a cached FDRef which
|
|
implicitly closes the fd once all references have expired.
|
|
|
|
Filestore syncs have a sideeffect of flushing all outstanding objects
|
|
in the wbthrottle.
|
|
|
|
lfn_unlink clears the cached FDRef and wbthrottle entries for the
|
|
unlinked object when the last link is removed and asserts that all
|
|
outstanding FDRefs for that object are dead.
|