On 10/12/2016 03:27 AM, Wang Xiaoguang wrote:
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,
I think you're right. I don't add new drive when doing my big files create and
delete test, so
it maybe "remove useless chunks" causing can_overcommit() returns true, but I
don't know
how to observe this in codes, sorry. And this patch can really help to fix my
enospc issue :)
Meanwhile, in shrink_delalloc(), if can_overcommit() returns true,
shrink_delalloc()
will not shrink delalloc bytes any more, in this case we should check whether
some tickcts' requests can overcommit, if some can, we can satisfy them timely
and directly.
I notice original btrfs codes before your patch "Btrfs: introduce ticketed
enospc infrastructure"
will have over_commit try when every flush_space() returns, so here we may also
need to do it, thanks.
Oh so you are deleting big files, that could free up block groups which would
make can_overcommit() suddenly start returning true. That makes sense. You can add
Reviewed-by: Josef Bacik <jba...@fb.com>
Thanks,
Josef
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html