Re: [PATCH 2/3] btrfs: wakeup cleaner thread when adding delayed iput

[Nikolay Borisov <nborisov@suse.com>]

On 21.11.18 г. 21:09 ч., Josef Bacik wrote:
> The cleaner thread usually takes care of delayed iputs, with the
> exception of the btrfs_end_transaction_throttle path.  The cleaner
> thread only gets woken up every 30 seconds, so instead wake it up to do
> it's work so that we can free up that space as quickly as possible.

Have you done any measurements how this affects the overall system. I
suspect this introduces a lot of noise since now we are going to be
doing a thread wakeup on every iput, does this give a chance to have
nice, large batches of iputs that  the cost of wake up can be amortized
across?

> 
> Reviewed-by: Filipe Manana <fdmanana@suse.com>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
>  fs/btrfs/inode.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 3da9ac463344..3c42d8887183 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3264,6 +3264,7 @@ void btrfs_add_delayed_iput(struct inode *inode)
>  	ASSERT(list_empty(&binode->delayed_iput));
>  	list_add_tail(&binode->delayed_iput, &fs_info->delayed_iputs);
>  	spin_unlock(&fs_info->delayed_iput_lock);
> +	wake_up_process(fs_info->cleaner_kthread);
>  }
>  
>  void btrfs_run_delayed_iputs(struct btrfs_fs_info *fs_info)
>