On Monday 04 May 2015 06:32 PM, Pratyush Anand wrote:
These patches add support for enable/disable d cache support. It reduces
time for sha verification from more than 2 min to 3-4 sec on my
platform.
There are some of the observation which I am unable to explain.
* It takes around 18 sec when I boot a kexec kernel and around 3-4 sec
* when I boot a crash kernel. In case of kexec kernel start of 1st
* segment is at 0000004000280000 and, end of last segment is at
* 00000040029c0000. In case of crash kernel start of 1st segment is at
* 00000041b9080000 and, end of last segment is at 00000041f9000000.
There is one more observation which is not explainable :(
While executing a secondary kernel using kexec -e, if sha256_process()
function is aligned at offset 256, it takes 18 sec else it takes double
ie 36 sec.
# objdump -d purgatory/purgatory.ro | grep sha256_process
0000000000001300 <sha256_process>:
-> takes 18 sec
If because of some changes in code, this function shifts a bit
# objdump -d purgatory/purgatory.ro | grep sha256_process
0000000000001310 <sha256_process>:
-> takes 36 sec.
So, "__attribute__ ((aligned (256))) void sha256_process(
sha256_context *ctx, const uint8_t data[64] )" guarantees constant
execution time, but how can this be justified?
~Pratyush
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