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Subject: [OMPI devel] knem_dma_min
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2010-08-18 13:15:39


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).