On Mon, 2011-11-21 at 17:18 +0800, Wu Fengguang wrote:

plain text document attachment (readahead-tracer.patch)
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 <redacted>
CC: Jens Axboe <redacted>
CC: Steven Rostedt <rostedt@goodmis.org>

Acked-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve

CC: Peter Zijlstra <redacted>
Acked-by: Rik van Riel <redacted>
Signed-off-by: Wu Fengguang <redacted>

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