Playin animation is so slow

i have 2000 frame animation. when i choose dope sheet/action editor and zoom out to see all 2000 keys blender play animation as 8 fps and frame rate is red(i think it means it cannot play it realtime). when i zoom in to see 10 frames range it plays 20 fps(red). when i choose info instead of dope sheet it plays 24 fps(white). i have just simple armature with 21 bones. there is no mesh.

is it normal? i have i7 macbook pro

Processor 2,3 GHz Intel Core i7
Memory 8 GB 1333 MHz DDR3
Graphics AMD Radeon HD 6750M 1024 MB

That happens with my computer. I think it does that so the program can handle it better.