Chris/Arnd,
Here is a series of test I did with the patched kernel.
== cold boot insert SD card ==
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
4MiB 4.96M/s
2MiB 6.3M/s
1MiB 6.23M/s
512KiB 6.23M/s
256KiB 6.26M/s
== rerun the same test 2nd time ===
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
4MiB 6.28M/s
2MiB 6.29M/s
1MiB 6.29M/s
512KiB 6.29M/s
256KiB 6.26M/s
== remove and reinsert the SD card ==
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
4MiB 6.42M/s
2MiB 6.28M/s
1MiB 6.22M/s
512KiB 6.23M/s
256KiB 6.26M/s
== remove and reinsert the SD card ==
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
4MiB 6.42M/s
2MiB 6.3M/s
1MiB 6.22M/s
512KiB 6.25M/s
256KiB 6.24M/s
== reboot, reinsert the SD card ==
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
[sudo] password for u:
4MiB 6.45M/s
2MiB 6.33M/s
1MiB 6.25M/s
512KiB 6.29M/s
256KiB 6.3M/s
u@u:~/flash/flashbench$
== rerun the test again ==
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
4MiB 6.27M/s
2MiB 6.27M/s
1MiB 6.28M/s
512KiB 6.27M/s
256KiB 6.24M/s
u@u:~/flash/flashbench$
== poweroff, Poweron, insert SD card ==
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
[sudo] password for u:
4MiB 6.45M/s
2MiB 6.33M/s
1MiB 6.24M/s
512KiB 6.29M/s
256KiB 6.32M/s
u@u:~/flash/flashbench$
== rerun the test again ==
u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 *
1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2
4MiB 6.29M/s
2MiB 6.28M/s
1MiB 6.29M/s
512KiB 6.28M/s
256KiB 6.25M/s
u@u:~/flash/flashbench$
On Wed, 13 Jul 2011, Chris Ball wrote:
Hi Arnd,
On Tue, Jul 12 2011, Arnd Bergmann wrote:
I would very much expect that to be nonreproducible. The first row
in each test is the result of a single write() system call and does
not get averaged out. More importantly the time for each write
depends a lot of the state of the card before the write.
For instance when you do a lot of random writes to a card, optionally
take it out and put it into a different machine, and then do a large
linear write, that linear write will be very slow because the
card has to garbage collect all the random writes that were done
earlier. After a few writes (usually one is enough), it gets back
to the full performance.
That makes sense. Do you think this explains Manoj getting a slower
first file copy speed (757ms vs. 480ms) after applying his patch?
(Manoj, perhaps you could retry your test without GC being needed?)
What would we expect lowering the SD base clock frequency from 200MHz
to 50MHz to do to performance theoretically?
Thanks,
- Chris.
--
Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/>
One Laptop Per Child
--
====================
Manoj Iyer
Ubuntu/Canonical
Hardware Enablement
====================
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