  We perform the first global QCD analysis of pion valence, sea quark, and
gluon distributions within a Bayesian Monte Carlo framework with threshold
resummation on Drell-Yan cross sections at next-to-leading log accuracy.
Exploring various treatments of resummation, we find that the large-$x$
asymptotics of the valence quark distribution $\sim (1-x)^{\beta_v}$ can differ
significantly, with $\beta_v$ ranging from $\approx 1$ to $> 2.5$ at the input
scale. Regardless of the specific implementation, however, the resummation
induced redistribution of the momentum between valence quarks and gluons boosts
the total momentum carried by gluons to $\approx 40\%$, increasing the gluon
contribution to the pion mass to $\approx 40$ MeV.
