  Limits on the size of quenched chiral logs in the pion mass for Wilson
fermions are investigated. The smallness of chiral logs is shown to be a result
of the suppression of the hairpin diagram for small $p^2$, such that the value
of the hairpin on the pion mass shell is much smaller than the physical
$m_{\eta'}^2$. A direct calculation of the topological susceptibility from the
same data gives $m_{\eta'}\approx 1$ GeV.
