(unknown charset) [TTM] Unable to allocate page

I am using "radeonkms" on a machine with quite mixed, diverse and varying loads.
Sometimes I get an X server crash like the following:

kernel: [TTM] Unable to allocate page
kernel: error: [drm:pid1815:radeon_gem_object_create] *ERROR* Failed to allocate
GEM object (25591808, 2, 4096, -12)
kernel: [TTM] Unable to allocate page
kernel: [TTM] Buffer eviction failed
kernel: vm_fault: pager read error, pid 1815 (Xorg)
kernel: pid 1815 (Xorg), uid 0: exited on signal 11 (core dumped)

At the same time there was the following in X servers stderr:
Failed to allocate :
   size      : 25589760 bytes
   alignment : 256 bytes
   domains   : 2

I wonder if this is a generic problem for example caused by severe resource
exhaustion or if this is something where FreeBSD specific code does not do its best.
In particular, it caught my attention that ttm_get_pages() effectively has
semantics of M_NOWAIT as it never retries allocation failures in
vm_page_alloc_contig().

-- 
Andriy Gapon