On Tue 29-11-11 21:09:07, Wu Fengguang wrote:
> This is very useful for verifying whether the readahead algorithms are
> working to the expectation.
>
> Example output:
>
> # echo 1 > /debug/tracing/events/vfs/readahead/enable
> # cp test-file /dev/null
> # cat /debug/tracing/trace # trimmed output
> readahead-initial(dev=0:15, ino=100177, req=0+2, ra=0+4-2, async=0) = 4
> readahead-subsequent(dev=0:15, ino=100177, req=2+2, ra=4+8-8, async=1) = 8
> readahead-subsequent(dev=0:15, ino=100177, req=4+2, ra=12+16-16, async=1) = 16
> readahead-subsequent(dev=0:15, ino=100177, req=12+2, ra=28+32-32, async=1) = 32
> readahead-subsequent(dev=0:15, ino=100177, req=28+2, ra=60+60-60, async=1) = 24
> readahead-subsequent(dev=0:15, ino=100177, req=60+2, ra=120+60-60, async=1) = 0
>
> CC: Ingo Molnar <mingo@xxxxxxx>
> CC: Jens Axboe <axboe@xxxxxxxxx>
> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
> CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Looks OK.
Acked-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> include/trace/events/vfs.h | 64 +++++++++++++++++++++++++++++++++++
> mm/readahead.c | 5 ++
> 2 files changed, 69 insertions(+)
>
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux-next/include/trace/events/vfs.h 2011-11-29 20:58:59.000000000 +0800
> @@ -0,0 +1,64 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM vfs
> +
> +#if !defined(_TRACE_VFS_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_VFS_H
> +
> +#include <linux/tracepoint.h>
> +
> +TRACE_EVENT(readahead,
> + TP_PROTO(struct address_space *mapping,
> + pgoff_t offset,
> + unsigned long req_size,
> + enum readahead_pattern pattern,
> + pgoff_t start,
> + unsigned long size,
> + unsigned long async_size,
> + unsigned int actual),
> +
> + TP_ARGS(mapping, offset, req_size, pattern, start, size, async_size,
> + actual),
> +
> + TP_STRUCT__entry(
> + __field( dev_t, dev )
> + __field( ino_t, ino )
> + __field( pgoff_t, offset )
> + __field( unsigned long, req_size )
> + __field( unsigned int, pattern )
> + __field( pgoff_t, start )
> + __field( unsigned int, size )
> + __field( unsigned int, async_size )
> + __field( unsigned int, actual )
> + ),
> +
> + TP_fast_assign(
> + __entry->dev = mapping->host->i_sb->s_dev;
> + __entry->ino = mapping->host->i_ino;
> + __entry->offset = offset;
> + __entry->req_size = req_size;
> + __entry->pattern = pattern;
> + __entry->start = start;
> + __entry->size = size;
> + __entry->async_size = async_size;
> + __entry->actual = actual;
> + ),
> +
> + TP_printk("readahead-%s(dev=%d:%d, ino=%lu, "
> + "req=%lu+%lu, ra=%lu+%d-%d, async=%d) = %d",
> + ra_pattern_names[__entry->pattern],
> + MAJOR(__entry->dev),
> + MINOR(__entry->dev),
> + __entry->ino,
> + __entry->offset,
> + __entry->req_size,
> + __entry->start,
> + __entry->size,
> + __entry->async_size,
> + __entry->start > __entry->offset,
> + __entry->actual)
> +);
> +
> +#endif /* _TRACE_VFS_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> --- linux-next.orig/mm/readahead.c 2011-11-29 20:58:53.000000000 +0800
> +++ linux-next/mm/readahead.c 2011-11-29 20:59:20.000000000 +0800
> @@ -29,6 +29,9 @@ static const char * const ra_pattern_nam
> [RA_PATTERN_ALL] = "all",
> };
>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/vfs.h>
> +
> /*
> * Initialise a struct file's readahead state. Assumes that the caller has
> * memset *ra to zero.
> @@ -215,6 +218,8 @@ static inline void readahead_event(struc
> for_mmap, for_metadata,
> pattern, start, size, async_size, actual);
> #endif
> + trace_readahead(mapping, offset, req_size,
> + pattern, start, size, async_size, actual);
> }
>
>
>
>
> --
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--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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