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The generic memcpy routine provided in kernel does only byte copies.
Using word copies we can lower boot time and cycles spend in memcpy
quite significantly.
Booting on my de0 nano I see boot times go from 7.2 to 5.6 seconds.
The avg cycles in memcpy during boot go from 6467 to 1887.
I tested several algorithms (see code in previous patch mails)
The implementations I tested and avg cycles:
- Word Copies + Loop Unrolls + Non Aligned 1882
- Word Copies + Loop Unrolls 1887
- Word Copies 2441
- Byte Copies + Loop Unrolls 6467
- Byte Copies 7600
In the end I ended up going with Word Copies + Loop Unrolls as it
provides best tradeoff between simplicity and boot speedups.
Signed-off-by: Stafford Horne <shorne@gmail.com>
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Clearing out one todo item. Use the memblock boot time memory
which is the current standard.
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Jonas <jonas@southpole.se>
Signed-off-by: Stafford Horne <shorne@gmail.com>
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Adds README file, TODO list, and a couple of other pieces that didn't seem
to fit into any other patch.
Signed-off-by: Jonas Bonn <jonas@southpole.se>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
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Stafford Horne
Jonas Bonn