Re: [PATCH 27/45] xfs: pass lv chain length into xlog_write()

Brian Foster
2021-03-16T18:39:50Z

On Fri, Mar 05, 2021 at 04:11:25PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> The caller of xlog_write() usually has a close accounting of the
> aggregated vector length contained in the log vector chain passed to
> xlog_write(). There is no need to iterate the chain to calculate he
> length of the data in xlog_write_calculate_len() if the caller is
> already iterating that chain to build it.
>
> Passing in the vector length avoids doing an extra chain iteration,
> which can be a significant amount of work given that large CIL
> commits can have hundreds of thousands of vectors attached to the
> chain.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_log.c | 37 ++++++-------------------------------
> fs/xfs/xfs_log_cil.c | 18 +++++++++++++-----
> fs/xfs/xfs_log_priv.h | 2 +-
> 3 files changed, 20 insertions(+), 37 deletions(-)
>
...
> diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
> index 7a5e6bdb7876..34abc3bae587 100644
> --- a/fs/xfs/xfs_log_cil.c
> +++ b/fs/xfs/xfs_log_cil.c
...
> @@ -893,6 +898,9 @@ xlog_cil_push_work(
> * transaction header here as it is not accounted for in xlog_write().
> */
> xlog_cil_build_trans_hdr(ctx, &thdr, &lvhdr, num_iovecs);
> + num_iovecs += lvhdr.lv_niovecs;

What's the point of this if num_iovecs is only used by
xlog_cil_build_trans_hdr()?

Brian

> + num_bytes += lvhdr.lv_bytes;
> +
>
> /*
> * Before we format and submit the first iclog, we have to ensure that
> @@ -907,7 +915,7 @@ xlog_cil_push_work(
> * write head.
> */
> error = xlog_write(log, &lvhdr, ctx->ticket, &ctx->start_lsn, NULL,
> - XLOG_START_TRANS);
> + XLOG_START_TRANS, num_bytes);
> if (error)
> goto out_abort_free_ticket;
>
> diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
> index 8ee6a5f74396..003c11653955 100644
> --- a/fs/xfs/xfs_log_priv.h
> +++ b/fs/xfs/xfs_log_priv.h
> @@ -462,7 +462,7 @@ void xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
> void xlog_print_trans(struct xfs_trans *);
> int xlog_write(struct xlog *log, struct xfs_log_vec *log_vector,
> struct xlog_ticket *tic, xfs_lsn_t *start_lsn,
> - struct xlog_in_core **commit_iclog, uint optype);
> + struct xlog_in_core **commit_iclog, uint optype, uint32_t len);
> int xlog_commit_record(struct xlog *log, struct xlog_ticket *ticket,
> struct xlog_in_core **iclog, xfs_lsn_t *lsn);
> void xlog_state_switch_iclogs(struct xlog *log, struct xlog_in_core *iclog,
> --
> 2.28.0
>