[PATCH 46/49] xfs: Combine CIL insert and prepare passes

[Mark Tinguely]

On 07/19/13 01:25, Dave Chinner wrote:
> From: Dave Chinner<dchinner at redhat.com>
>
> Now that all the log item preparation and formatting is done under
> the CIL lock, we can get rid of the intermediate log vector chain
> used to track items to be inserted into the CIL.
>
> We can already find all the items to be committed from the
> transaction handle, so as long as we attach the log vectors to the
> item before we insert the items into the CIL, we don't need to
> create a log vector chain to pass around.
>
> This means we can move all the item insertion code into and optimise
> it into a pair of simple passes across all the items in the
> transaction. The first pass does the formatting and accounting, the
> second inserts them all into the CIL.
>
> We keep this two pass split so that we can separate the CIL
> insertion - which must be done under the CIL spinlock - from the
> formatting. We could insert each item into the CIL with a single
> pass, but that massively increases the number of times we have to
> grab the CIL spinlock. It is much more efficient (and hence
> scalable) to do a batch operation and insert all objects in a single
> lock grab.
>
> Signed-off-by: Dave Chinner<dchinner at redhat.com>

...

> @@ -357,10 +341,8 @@ xlog_cil_insert_items(
>   	 * during the transaction commit.
>   	 */
>   	if (ctx->ticket->t_curr_res == 0) {
> -		/* first commit in checkpoint, steal the header reservation */
> -		ASSERT(ticket->t_curr_res>= ctx->ticket->t_unit_res + len);

^^ is the ctx ticket overflow caught somewhere else? ^^^^

>   		ctx->ticket->t_curr_res = ctx->ticket->t_unit_res;
> -		ticket->t_curr_res -= ctx->ticket->t_unit_res;
> +		tp->t_ticket->t_curr_res -= ctx->ticket->t_unit_res;
>   	}
>

Thanks,

--Mark.