Wow. That took you so much cognition. No, it's not, if you have hardware sitting otherwise 'idle'. Besides, if you have a GPU, you're better off mining pretty much any other coin (above SM_3.0 capable cards only - Cryptonight is still worthwhile on older cards - 770s, etc)

9 kH/s gets me 0.0033 BTC / day payout on Nicehash which is not insignificant. Make sure you arrange your cores correctly to use the cache for each CPU package - Linux arranges them as (4 cores, 8 threads)
Package 1      |  Package 2
0   1   2   3     |  4   5   6  7 (HT1)
8   9   10 11  |    12 13 14 15 (HT2)

So as an example if you need 6 threads per CPU package to fill your cache,  fill all of one HT set on both package, then fill it out with additional HT cores.

That would be affinity set to (Package 1) 0,1,2,3,  (Package 2)  4,5,6,7, (Package 1) 8,9,   (Package 2) 12,13

If you are only mining with the box, you get better heat efficiency by turning off cores in the BIOS + using larger threads (above assumes xmr-stak-cpu)

Cheers!