  We study the use of NLO and NNLO formulae from SU(2) chiral perturbation
theory to fit results from the 2+1 flavor DWF QCD ensembles that have been
generated by the RBC and UKQCD collaborations. These ensembles are at two
different lattice spacings, contain multiple dynamical light quark masses, and
include a variety of partially quenched valence quark masses. Both NLO and
complete NNLO fits well represent our data, which has m_pi in the range 220 to
420 MeV. With our data, the NNLO fits have NLO and NNLO contributions of
similar size, making the series not convergent and the extrapolation to
physical light quark masses imprecise. Thus, we use NLO fit results for our
predictions of f_pi, f_K and the light quark masses.
