hi,
On 10/07/2016 09:16 PM, Josef Bacik wrote:
On 09/21/2016 02:59 AM, Wang Xiaoguang wrote:
In flush_space()->shrink_delalloc(), if can_overcommit() returns true,
though no bytes added to space_info, we still may satisfy some requests.
Signed-off-by: Wang Xiaoguang <wangxg.f...@cn.fujitsu.com>
---
fs/btrfs/extent-tree.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 38c2df8..fdfc97f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4960,6 +4960,43 @@ static void wake_all_tickets(struct list_head
*head)
}
/*
+ * This function must be protected by btrfs_space_info's lock.
+ */
+static void try_to_wake_tickets(struct btrfs_root *root,
+ struct btrfs_space_info *space_info)
+{
+ struct reserve_ticket *ticket;
+ struct list_head *head = &space_info->priority_tickets;
+ enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_NO_FLUSH;
+ u64 used;
+
+again:
+ while (!list_empty(head)) {
+ ticket = list_first_entry(head, struct reserve_ticket,
+ list);
+ used = space_info->bytes_used +
+ space_info->bytes_reserved + space_info->bytes_pinned +
+ space_info->bytes_readonly + space_info->bytes_may_use;
+
+ if (used + ticket->bytes <= space_info->total_bytes ||
+ can_overcommit(root, space_info, ticket->bytes, flush)) {
+ space_info->bytes_may_use += ticket->bytes;
+ list_del_init(&ticket->list);
+ ticket->bytes = 0;
+ space_info->tickets_id++;
+ wake_up(&ticket->wait);
+ } else
+ return;
+ }
+
+ if (head == &space_info->priority_tickets) {
+ head = &space_info->tickets;
+ flush = BTRFS_RESERVE_FLUSH_ALL;
+ goto again;
+ }
+}
+
+/*
* This is for normal flushers, we can wait all goddamned day if we
want to. We
* will loop and continuously try to flush as long as we are making
progress.
* We count progress as clearing off tickets each time we have to loop.
@@ -4995,6 +5032,8 @@ static void
btrfs_async_reclaim_metadata_space(struct work_struct *work)
ret = flush_space(fs_info->fs_root, space_info, to_reclaim,
to_reclaim, flush_state);
spin_lock(&space_info->lock);
+ if (!ret)
+ try_to_wake_tickets(fs_info->fs_root, space_info);
if (list_empty(&space_info->tickets)) {
space_info->flush = 0;
spin_unlock(&space_info->lock);
So first off I have no problems with this patch, it seems reasonable
to me.
However I'm curious to see where it helped. The only time
can_overcommit() would suddenly start returning true where it wouldn't
have before without actually adding space to the space_info would be
when we've dropped an empty block group (or added a new drive) and
suddenly fs_info->free_chunk_space is larger than it was. Is that
what you were observing? Thanks,
Indeed, I'm not sure :)
I just found can_overcommit() sometimes can help, I'll run some tests
and inform you what's happening later.
Regards,
Xiaoguang Wang
Josef
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