Re: [PATCH] jbd2: Increase IO priority of checkpoint.

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

Julian Sun <sunjunchao@bytedance.com> writes:

> In commit 6a3afb6ac6df ("jbd2: increase the journal IO's priority"),
> the priority of IOs initiated by jbd2 has been raised, exempting them
> from WBT throttling.
> Checkpoint is also a crucial operation of jbd2. While no serious issues
> have been observed so far, it should still be reasonable to exempt
> checkpoint from WBT throttling.
>

Interesting.. I was wondering whether we were able to observe any
throttling for jbd2 log writes or for jbd2 checkpoint?
Maybe It would have been nice, if we had some kind of data for this. 

BTW - does it make sense for fastcommit path too maybe for non-tail
fc write requests? I think it uses ext4_fc_submit_bh(). 

-ritesh


> Signed-off-by: Julian Sun <sunjunchao@bytedance.com>
> ---
>  fs/jbd2/checkpoint.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
> index 38861ca04899..2d0719bf6d87 100644
> --- a/fs/jbd2/checkpoint.c
> +++ b/fs/jbd2/checkpoint.c
> @@ -131,7 +131,7 @@ __flush_batch(journal_t *journal, int *batch_count)
>  
>  	blk_start_plug(&plug);
>  	for (i = 0; i < *batch_count; i++)
> -		write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
> +		write_dirty_buffer(journal->j_chkpt_bhs[i], JBD2_JOURNAL_REQ_FLAGS);
>  	blk_finish_plug(&plug);
>  
>  	for (i = 0; i < *batch_count; i++) {
> -- 
> 2.20.1