  Currently, the gluon distribution function is mainly constrained by jet data.
Yet, its high-x behaviour is largely unknown. This kinematic region is
important, for instance, for the understanding of the production of a massive
state at forward rapidities at the LHC. In the past, single inclusive direct
photon data from fixed target experiments was used to constrain the gluon
distribution due to its dominant contribution from the $qg \rightarrow\gamma q$
subprocess in proton-proton collisions. Due to disagreement with its
theoretical predictions at next-to-leading order (NLO) in perturbative QCD
(pQCD), direct photon data have been excluded from global fits. This talk will
discuss an improvement to such theoretical predictions by including
\emph{threshold resummation} at next-to-leading logarithmic accuracy (NLL) and
its impact on gluon distribution at large-x using Bayesian reweighting
technique.
