This is very useful for verifying whether the algorithms are working to our expectaions. 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 CC: Jens Axboe CC: Steven Rostedt CC: Peter Zijlstra Acked-by: Rik van Riel Signed-off-by: Wu Fengguang --- 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 2011-11-21 17:17:45.000000000 +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 + +TRACE_EVENT(readahead, + TP_PROTO(struct address_space *mapping, + pgoff_t offset, + unsigned long req_size, + unsigned int ra_flags, + pgoff_t start, + unsigned int size, + unsigned int async_size, + unsigned int actual), + + TP_ARGS(mapping, offset, req_size, + ra_flags, 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->pattern = ra_pattern(ra_flags); + __entry->offset = offset; + __entry->req_size = req_size; + __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 --- linux-next.orig/mm/readahead.c 2011-11-21 17:17:45.000000000 +0800 +++ linux-next/mm/readahead.c 2011-11-21 17:17:49.000000000 +0800 @@ -48,6 +48,9 @@ static int __init config_readahead_size( } early_param("readahead", config_readahead_size); +#define CREATE_TRACE_POINTS +#include + /* * Initialise a struct file's readahead state. Assumes that the caller has * memset *ra to zero. @@ -236,6 +239,8 @@ static void readahead_event(struct addre start, size, async_size, actual); } #endif + trace_readahead(mapping, offset, req_size, ra_flags, + start, size, async_size, actual); } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/