2016-05-20 5:20 GMT+09:00 Thomas Garnier [off-list ref]:

I ran the test given by Joonsoo and it gave me these minimum cycles
per size across 20 usage:

I can't understand what you did here. Maybe, it's due to my poor Engling.
Please explain more. You did single thread test? Why minimum cycles
rather than average?

size,before,after
8,63.00,64.50 (102.38%)
16,64.50,65.00 (100.78%)
32,65.00,65.00 (100.00%)
64,66.00,65.00 (98.48%)
128,66.00,65.00 (98.48%)
256,64.00,64.00 (100.00%)
512,65.00,66.00 (101.54%)
1024,68.00,64.00 (94.12%)
2048,66.00,65.00 (98.48%)
4096,66.00,66.00 (100.00%)

It looks like performance of all size classes are the same?

I assume the difference is bigger if you don't have RDRAND support.

What does RDRAND means? Kconfig? How can I check if I have RDRAND?

Christoph, Joonsoo: Do you think it would be valuable to add a CONFIG
to disable additional randomization per new page? It will remove
additional entropy but increase performance for machines without arch
specific randomization instructions.

I don't think that it deserve another CONFIG. If performance is a matter,
I think that removing additional entropy is better until it is proved that
entropy is a problem.

Thanks.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>