Re: [PATCH 01/11] iomap: add tracing for the readpage / readpages

[Darrick J. Wong]

On Tue, Oct 01, 2019 at 09:11:42AM +0200, Christoph Hellwig wrote:
> Lift the xfs code for tracing address space operations to the iomap
> layer.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>  fs/iomap/buffered-io.c       |  7 +++++++
>  include/trace/events/iomap.h | 27 +++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+)
>  create mode 100644 include/trace/events/iomap.h
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index e25901ae3ff4..099daf0c09b8 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -19,6 +19,9 @@
>  
>  #include "../internal.h"
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/iomap.h>
> +
>  static struct iomap_page *
>  iomap_page_create(struct inode *inode, struct page *page)
>  {
> @@ -293,6 +296,8 @@ iomap_readpage(struct page *page, const struct iomap_ops *ops)
>  	unsigned poff;
>  	loff_t ret;
>  
> +	trace_iomap_readpage(page->mapping->host, 1);
> +
>  	for (poff = 0; poff < PAGE_SIZE; poff += ret) {
>  		ret = iomap_apply(inode, page_offset(page) + poff,
>  				PAGE_SIZE - poff, 0, ops, &ctx,
> @@ -389,6 +394,8 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages,
>  	loff_t last = page_offset(list_entry(pages->next, struct page, lru));
>  	loff_t length = last - pos + PAGE_SIZE, ret = 0;
>  
> +	trace_iomap_readpages(mapping->host, nr_pages);
> +
>  	while (length > 0) {
>  		ret = iomap_apply(mapping->host, pos, length, 0, ops,
>  				&ctx, iomap_readpages_actor);
> diff --git a/include/trace/events/iomap.h b/include/trace/events/iomap.h
> new file mode 100644
> index 000000000000..7d2fe2c773f3
> --- /dev/null
> +++ b/include/trace/events/iomap.h

...and I guess while we're bikeshedding over tracepoints, why not put
this in fs/iomap/trace.h ?  Do you anticipate anyone outside of iomap
needing to access the tracepoint declarations?

--D

> @@ -0,0 +1,27 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2009-2019, Christoph Hellwig
> + * All Rights Reserved.
> + *
> + * NOTE: none of these tracepoints shall be consider a stable kernel ABI
> + * as they can change at any time.
> + */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM iomap
> +
> +#if !defined(_TRACE_IOMAP_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_IOMAP_H
> +
> +#include <linux/tracepoint.h>
> +
> +#define DEFINE_READPAGE_EVENT(name)		\
> +DEFINE_EVENT(iomap_readpage_class, name,	\
> +	TP_PROTO(struct inode *inode, int nr_pages), \
> +	TP_ARGS(inode, nr_pages))
> +DEFINE_READPAGE_EVENT(iomap_readpage);
> +DEFINE_READPAGE_EVENT(iomap_readpages);
> +
> +#endif /* _TRACE_IOMAP_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> -- 
> 2.20.1
>