[dm-devel] [PATCH 0/2] Introduce the request handling for dm-crypt

[Arnd Bergmann]

On Friday 13 November 2015 10:05:28 Baolin Wang wrote:
> 
> Well, I did a simple test with dd reading, cause my engine limitation is 1M,
> (1) so the time like below when handle 1M at one time.
> 1048576 bytes (1.0 MB) copied, 0.0841235 s, 12.5 MB/s
> 1048576 bytes (1.0 MB) copied, 0.0836294 s, 12.5 MB/s
> 1048576 bytes (1.0 MB) copied, 0.0836526 s, 12.5 MB/s
> 
> (2) These handle 64K at one time * 16 times
> 1048576 bytes (1.0 MB) copied, 0.0937223 s, 11.2 MB/s
> 1048576 bytes (1.0 MB) copied, 0.097205 s, 10.8 MB/s
> 1048576 bytes (1.0 MB) copied, 0.0935884 s, 11.2 MB/s
> 
> Here is a 10ms level difference, try to image if the hardware engine's
> throughput is bigger than that. But like Jens said, we can measure it
> by the performance data.

The absolute numbers look really low. Does this include writing to
a hard drive? That would certainly make the difference appear
less significant.

Could you try backing this with a ram disk backing for comparison,
and also use 'time dd' to show the CPU utilization for all cases?
For completeness, including cpu-only performance might also help
put this into perspective.

	Arnd