Re: [PATCH 1/1] xfs: add trace points for xlog cil operations

[Brian Foster <bfoster@redhat.com>]

On Thu, May 18, 2017 at 10:49:51AM +0800, Shan Hai wrote:
> Signed-off-by: Shan Hai <shan.hai@oracle.com>
> ---

Any particular reason you're looking for these new tracepoints (i.e., a
commit log would be nice ;).

>  fs/xfs/xfs_log_cil.c | 16 +++++++++++++++-
>  fs/xfs/xfs_trace.h   | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
> index 10309cf..f2cf0fe 100644
> --- a/fs/xfs/xfs_log_cil.c
> +++ b/fs/xfs/xfs_log_cil.c
> @@ -579,6 +579,8 @@
>  	xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
>  					ctx->start_lsn, abort);
>  
> +	trace_xlog_cil_committed(ctx->cil, ctx);
> +

FWIW, I think we tend to put these kind of function call tracepoints at
or towards the beginning of the associated function.

>  	xfs_extent_busy_sort(&ctx->busy_extents);
>  	xfs_extent_busy_clear(mp, &ctx->busy_extents,
>  			     (mp->m_flags & XFS_MOUNT_DISCARD) && !abort);
> @@ -841,6 +843,8 @@
>  	wake_up_all(&cil->xc_commit_wait);
>  	spin_unlock(&cil->xc_push_lock);
>  
> +	trace_xlog_cil_push(cil, ctx);
> +
>  	/* release the hounds! */
>  	return xfs_log_release_iclog(log->l_mp, commit_iclog);
>  
> @@ -898,7 +902,8 @@
>  		queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);
>  	}
>  	spin_unlock(&cil->xc_push_lock);
> -
> +	
> +	trace_xlog_cil_push_background(cil, cil->xc_ctx);

Whitespace damage above.

And do we really need the ctx information for all of these tp's? It
looks like some of these could be racy (i.e., _push_now()). FWIW,
_push_background() and _push_now() both seem like a bit of overkill to
me as well.

>  }
>  
>  /*
> @@ -935,6 +940,8 @@
>  	cil->xc_push_seq = push_seq;
>  	queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);
>  	spin_unlock(&cil->xc_push_lock);
> +
> +	trace_xlog_cil_push_now(cil, cil->xc_ctx);
>  }
>  
>  bool
> @@ -1011,6 +1018,8 @@
>  	 */
>  	xfs_trans_free_items(tp, xc_commit_lsn, false);
>  
> +	trace_xfs_log_commit_cil(cil, cil->xc_ctx);
> +
>  	xlog_cil_push_background(log);
>  
>  	up_read(&cil->xc_ctx_lock);
> @@ -1037,6 +1046,8 @@
>  
>  	ASSERT(sequence <= cil->xc_current_sequence);
>  
> +	trace_xlog_cil_force_lsn(cil, cil->xc_ctx);
> +

Racy (what stabilizes xc_ctx)? Also, why wouldn't we want the sequence
value here?

>  	/*
>  	 * check to see if we need to force out the current context.
>  	 * xlog_cil_push() handles racing pushes for the same sequence,
> @@ -1098,6 +1109,9 @@
>  	}
>  
>  	spin_unlock(&cil->xc_push_lock);
> +
> +	trace_xlog_cil_force_lsn_exit(cil, cil->xc_ctx);
> +
>  	return commit_lsn;
>  
>  	/*
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 0712eb7..8d0cb73 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -37,6 +37,8 @@
>  struct xlog_recover_item;
>  struct xfs_buf_log_format;
>  struct xfs_inode_log_format;
> +struct xfs_cil;
> +struct xfs_cil_ctx;
>  struct xfs_bmbt_irec;
>  struct xfs_btree_cur;
>  struct xfs_refcount_irec;
> @@ -1112,6 +1114,53 @@
>  DEFINE_AIL_EVENT(xfs_ail_move);
>  DEFINE_AIL_EVENT(xfs_ail_delete);
>  
> +DECLARE_EVENT_CLASS(xfs_cil_class,
> +	TP_PROTO(struct xfs_cil *cil, struct xfs_cil_ctx *ctx),
> +	TP_ARGS(cil, ctx),
> +	TP_STRUCT__entry(
> +		__field(struct xfs_cil *, cil)
> +		__field(xfs_lsn_t, push_seq)
> +		__field(xfs_lsn_t, curr_seq)
> +		__field(xfs_lsn_t, chkpt_seq)
> +		__field(xfs_lsn_t, start_lsn)
> +		__field(xfs_lsn_t, commit_lsn)
> +		__field(int, nvecs)
> +		__field(int, space_used)
> +	),
> +	TP_fast_assign(
> +		__entry->cil = cil;
> +		__entry->push_seq = cil->xc_push_seq;
> +		__entry->curr_seq = cil->xc_current_sequence;
> +		__entry->chkpt_seq = ctx->sequence;
> +		__entry->start_lsn = ctx->start_lsn;
> +		__entry->commit_lsn = ctx->commit_lsn;
> +		__entry->nvecs = ctx->nvecs;
> +		__entry->space_used = ctx->space_used;
> +	),
> +	TP_printk("cil 0x%p push_seq %d/%d current_seq %d/%d chkpt_seq %d/%d "
> +		  "start_lsn %d/%d commit_lsn %d/%d nvecs %d space_used %d",
> +		  __entry->cil,

We need to print the "dev %d:%d" major/minor pair first so the
tracepoints can be correlated to a specific mount.

Brian

> +		  CYCLE_LSN(__entry->push_seq), BLOCK_LSN(__entry->push_seq),
> +		  CYCLE_LSN(__entry->curr_seq), BLOCK_LSN(__entry->curr_seq),
> +		  CYCLE_LSN(__entry->chkpt_seq), BLOCK_LSN(__entry->chkpt_seq),
> +		  CYCLE_LSN(__entry->start_lsn), BLOCK_LSN(__entry->start_lsn),
> +		  CYCLE_LSN(__entry->commit_lsn),
> +		  BLOCK_LSN(__entry->commit_lsn),
> +		  __entry->nvecs, __entry->space_used)
> +)
> +
> +#define DEFINE_CIL_EVENT(name) \
> +DEFINE_EVENT(xfs_cil_class, name, \
> +	TP_PROTO(struct xfs_cil *cil, struct xfs_cil_ctx *ctx), \
> +	TP_ARGS(cil, ctx))
> +DEFINE_CIL_EVENT(xlog_cil_push);
> +DEFINE_CIL_EVENT(xlog_cil_push_now);
> +DEFINE_CIL_EVENT(xlog_cil_push_background);
> +DEFINE_CIL_EVENT(xlog_cil_force_lsn);
> +DEFINE_CIL_EVENT(xlog_cil_force_lsn_exit);
> +DEFINE_CIL_EVENT(xlog_cil_committed);
> +DEFINE_CIL_EVENT(xfs_log_commit_cil);
> +
>  TRACE_EVENT(xfs_log_assign_tail_lsn,
>  	TP_PROTO(struct xlog *log, xfs_lsn_t new_lsn),
>  	TP_ARGS(log, new_lsn),
> -- 
> 1.8.3.1
> 
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