In mca_btl_sm_get_sync(), I see this:
/* Use the DMA flag if knem supports it *and* the segment length
is greater than the cutoff. Note that if the knem_dma_min
value is 0 (i.e., the MCA param was set to 0), the segment size
will never be larger than it, so DMA will never be used. */
icopy.flags = 0;
if (mca_btl_sm_component.knem_dma_min <= dst->seg_len) {
icopy.flags = mca_btl_sm_component.knem_dma_flag;
}
I'm going to poke around some more, but this doesn't on the surface make
sense to me. If knem_dma_min==0, it would seem as though the segment
size will *always* be at least that large and DMA will *always* be used
(if supported).
