Thank you for your advices!
I develop mobile app with unity 2018.1 and latest spine-unity 3.6 runtime.
I'm sorry, I am prohibited to share our products. I took a screen shot.

I made a test on iPodTouch 6th generation.
I put 100 skeletons in scene. (at 3448 fps)
I made a clone and edited json to change curve to linear. (at 3852 fps)
I removed 3 unnecessary timeline from original json.(at 3753 fps)
I changed curve to linear. (at 4155 fps)
And I profiled this test.
CurveTimeline.GetCurvePercent took 1.5%4% of CPU Time.
I think it's not actually the bottle neck, but I was able to improve the performance a little.
Thank you!