Perhaps there are scenarios where larger buffers are useful; I supppose getting an interrupt every 4 kilobytes transferred could be a decent performance hit wit

Perhaps there are scenarios where larger buffers are useful; I supppose getting an interrupt every 4 kilobytes transferred could be a decent performance hit with some devices, like a hardware /dev/null accelerator. If these numbers are what I think they are, then in my systems it's not used a lot: % sudo grep . /sys/kernel/debug/swiotlb/{io_tlb_nslabs,io_tlb_used} /sys/kernel/debug/swiotlb/io_tlb_nslabs:32768 /sys/kernel/debug/swiotlb/io_tlb_used:4 My other systems used 0-2.