diff options
author | Qu Wenruo <quwenruo@cn.fujitsu.com> | 2017-02-15 10:43:03 +0800 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2017-02-17 12:03:55 +0100 |
commit | fb235dc06fac9eaa4408ade9c8b20d45d63c89b7 (patch) | |
tree | 2bd827b257ac580b31097fa13a98bab3a0162c9e /fs/btrfs/qgroup.h | |
parent | 15b34517a6368c607ae7fd51c24cdc69efcd47fc (diff) | |
download | linux-fb235dc06fac9eaa4408ade9c8b20d45d63c89b7.tar.bz2 |
btrfs: qgroup: Move half of the qgroup accounting time out of commit trans
Just as Filipe pointed out, the most time consuming parts of qgroup are
btrfs_qgroup_account_extents() and
btrfs_qgroup_prepare_account_extents().
Which both call btrfs_find_all_roots() to get old_roots and new_roots
ulist.
What makes things worse is, we're calling that expensive
btrfs_find_all_roots() at transaction committing time with
TRANS_STATE_COMMIT_DOING, which will blocks all incoming transaction.
Such behavior is necessary for @new_roots search as current
btrfs_find_all_roots() can't do it correctly so we do call it just
before switch commit roots.
However for @old_roots search, it's not necessary as such search is
based on commit_root, so it will always be correct and we can move it
out of transaction committing.
This patch moves the @old_roots search part out of
commit_transaction(), so in theory we can half the time qgroup time
consumption at commit_transaction().
But please note that, this won't speedup qgroup overall, the total time
consumption is still the same, just reduce the performance stall.
Cc: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/qgroup.h')
-rw-r--r-- | fs/btrfs/qgroup.h | 33 |
1 files changed, 30 insertions, 3 deletions
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h index ee95f456a61f..26932a8a1993 100644 --- a/fs/btrfs/qgroup.h +++ b/fs/btrfs/qgroup.h @@ -94,9 +94,10 @@ int btrfs_qgroup_prepare_account_extents(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info); /* * Inform qgroup to trace one dirty extent, its info is recorded in @record. - * So qgroup can account it at commit trans time. + * So qgroup can account it at transaction committing time. * - * No lock version, caller must acquire delayed ref lock and allocate memory. + * No lock version, caller must acquire delayed ref lock and allocated memory, + * then call btrfs_qgroup_trace_extent_post() after exiting lock context. * * Return 0 for success insert * Return >0 for existing record, caller can free @record safely. @@ -108,11 +109,37 @@ int btrfs_qgroup_trace_extent_nolock( struct btrfs_qgroup_extent_record *record); /* + * Post handler after qgroup_trace_extent_nolock(). + * + * NOTE: Current qgroup does the expensive backref walk at transaction + * committing time with TRANS_STATE_COMMIT_DOING, this blocks incoming + * new transaction. + * This is designed to allow btrfs_find_all_roots() to get correct new_roots + * result. + * + * However for old_roots there is no need to do backref walk at that time, + * since we search commit roots to walk backref and result will always be + * correct. + * + * Due to the nature of no lock version, we can't do backref there. + * So we must call btrfs_qgroup_trace_extent_post() after exiting + * spinlock context. + * + * TODO: If we can fix and prove btrfs_find_all_roots() can get correct result + * using current root, then we can move all expensive backref walk out of + * transaction committing, but not now as qgroup accounting will be wrong again. + */ +int btrfs_qgroup_trace_extent_post(struct btrfs_fs_info *fs_info, + struct btrfs_qgroup_extent_record *qrecord); + +/* * Inform qgroup to trace one dirty extent, specified by @bytenr and * @num_bytes. * So qgroup can account it at commit trans time. * - * Better encapsulated version. + * Better encapsulated version, with memory allocation and backref walk for + * commit roots. + * So this can sleep. * * Return 0 if the operation is done. * Return <0 for error, like memory allocation failure or invalid parameter |