When checking out the performance data on the apiserver under soak testing it appears that there is a fair amount of gc work going on:

20.43% kube-apiserver [.] runtime.MSpan_Sweep
3.91% kube-apiserver [.] findrunnable
3.05% kube-apiserver [.] runtime.mallocgc
2.29% kube-apiserver [.] scanblock
1.83% kube-apiserver [.] runtime.sweepone
1.75% kube-apiserver [.] runtime.atomicload
1.73% kube-apiserver [.] runtime.xchg
1.54% kube-apiserver [.] runtime.duffcopy
1.47% kube-apiserver [.] flushptrbuf
1.22% kube-apiserver [.] runtime.memclr
1.19% kube-apiserver [.] runqgrab

Seems related to: golang/go#9265

go version go1.3.3 linux/amd64