11-22-2008
Help with __builtin_prefetch function and it's timing
Hello there, I just needed to know how to get the timing right when using the gcc __builtin_prefetch() function, that is, how many instructions before the actual utilization of the data should I make the prefetch call.
I will be measuring the L1 cache hit rate with valgrind's cachegrind, simulating a 1KB L1 Data cache.
Just in case you ask yourself what's the point in doing what I'm doing, I tell you it's a university project.
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LEARN ABOUT MINIX
cg_annotate
CG_ANNOTATE(1) Release 3.7.0 CG_ANNOTATE(1)
NAME
cg_annotate - post-processing tool for Cachegrind
SYNOPSIS
cg_annotate [options] cachegrind-out-file [source-files...]
DESCRIPTION
cg_annotate takes an output file produced by the Valgrind tool Cachegrind and prints the information in an easy-to-read form.
OPTIONS
-h --help
Show the help message.
--version
Show the version number.
--show=A,B,C [default: all, using order in cachegrind.out.<pid>]
Specifies which events to show (and the column order). Default is to use all present in the cachegrind.out.<pid> file (and use the
order in the file). Useful if you want to concentrate on, for example, I cache misses (--show=I1mr,ILmr), or data read misses
(--show=D1mr,DLmr), or LL data misses (--show=DLmr,DLmw). Best used in conjunction with --sort.
--sort=A,B,C [default: order in cachegrind.out.<pid>]
Specifies the events upon which the sorting of the function-by-function entries will be based.
--threshold=X [default: 0.1%]
Sets the threshold for the function-by-function summary. A function is shown if it accounts for more than X% of the counts for the
primary sort event. If auto-annotating, also affects which files are annotated.
Note: thresholds can be set for more than one of the events by appending any events for the --sort option with a colon and a number (no
spaces, though). E.g. if you want to see each function that covers more than 1% of LL read misses or 1% of LL write misses, use this
option:
--sort=DLmr:1,DLmw:1
--auto=<no|yes> [default: no]
When enabled, automatically annotates every file that is mentioned in the function-by-function summary that can be found. Also gives a
list of those that couldn't be found.
--context=N [default: 8]
Print N lines of context before and after each annotated line. Avoids printing large sections of source files that were not executed.
Use a large number (e.g. 100000) to show all source lines.
-I<dir> --include=<dir> [default: none]
Adds a directory to the list in which to search for files. Multiple -I/--include options can be given to add multiple directories.
SEE ALSO
valgrind(1), $INSTALL/share/doc/valgrind/html/index.html or http://www.valgrind.org/docs/manual/index.html.
AUTHOR
Nicholas Nethercote.
Release 3.7.0 06/05/2012 CG_ANNOTATE(1)