Re: [PATCH 37/45] xfs: track CIL ticket reservation in percpu structure

Darrick J. Wong
2021-03-11T00:26:59Z

On Fri, Mar 05, 2021 at 04:11:35PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> To get it out from under the cil spinlock.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_log_cil.c | 11 ++++++-----
> fs/xfs/xfs_log_priv.h | 2 +-
> 2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
> index 5519d112c1fd..a2f93bd7644b 100644
> --- a/fs/xfs/xfs_log_cil.c
> +++ b/fs/xfs/xfs_log_cil.c
> @@ -492,6 +492,7 @@ xlog_cil_insert_items(
> * based on how close we are to the hard limit.
> */
> cilpcp = get_cpu_ptr(cil->xc_pcp);
> + cilpcp->space_reserved += ctx_res;
> cilpcp->space_used += len;
> if (space_used >= XLOG_CIL_SPACE_LIMIT(log) ||
> cilpcp->space_used >
> @@ -502,10 +503,6 @@ xlog_cil_insert_items(
> }
> put_cpu_ptr(cilpcp);
>
> - spin_lock(&cil->xc_cil_lock);
> - ctx->ticket->t_unit_res += ctx_res;
> - ctx->ticket->t_curr_res += ctx_res;
> -
> /*
> * If we've overrun the reservation, dump the tx details before we move
> * the log items. Shutdown is imminent...
> @@ -527,6 +524,7 @@ xlog_cil_insert_items(
> * We do this here so we only need to take the CIL lock once during
> * the transaction commit.
> */
> + spin_lock(&cil->xc_cil_lock);
> list_for_each_entry(lip, &tp->t_items, li_trans) {
>
> /* Skip items which aren't dirty in this transaction. */
> @@ -798,10 +796,13 @@ xlog_cil_push_work(
>
> down_write(&cil->xc_ctx_lock);
>
> - /* Reset the CIL pcp counters */
> + /* Aggregate and reset the CIL pcp counters */
> for_each_online_cpu(cpu) {
> cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
> + ctx->ticket->t_curr_res += cilpcp->space_reserved;

Why isn't it necessary to update ctx->ticket->t_unit_res any more?

(Admittedly I'm struggling to figure out why it matters to keep it
updated even in the current code base...)

--D

> cilpcp->space_used = 0;
> + cilpcp->space_reserved = 0;
> +
> }
>
> spin_lock(&cil->xc_push_lock);
> diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
> index 4eb373357f26..278b9eaea582 100644
> --- a/fs/xfs/xfs_log_priv.h
> +++ b/fs/xfs/xfs_log_priv.h
> @@ -236,7 +236,7 @@ struct xfs_cil_ctx {
> */
> struct xlog_cil_pcp {
> uint32_t space_used;
> - uint32_t curr_res;
> + uint32_t space_reserved;
> struct list_head busy_extents;
> struct list_head log_items;
> };
> --
> 2.28.0
>