git: kernel - Increase DMA reserve from 16M to 128M by default

Matthew Dillon dillon at
Tue Jun 9 08:42:03 PDT 2015

commit 5a05c8a560a4394667e763ff5c7166c14978a630
Author: Matthew Dillon <dillon at>
Date:   Tue Jun 9 08:36:15 2015 -0700

    kernel - Increase DMA reserve from 16M to 128M by default
    * People running DragonFly on workstations were having to specify
      more than the default 16M for vm.dma_reserved in /boot/loader.conf
      or their X sessions would not be stable.
    * To reduce confusion, the dma_reserved default is being increased
      to 128M which should be sufficient for most display setups.
      People with headless servers will have to explicitly reduce the
      reservation in /boot/loader.conf (back to 16m is my suggestions) if
      they wish to recover the memory.
    * This is the best compromise I could think of.  We can't just return
      the memory to the pool after boot because X might be started far later
      on, or even potentially killed and restarted.  Other drivers might also
      depend on large swaths of contiguous physical memory being available.
      The reserve is the best way to do it and I would rather things work out
      of the box rather than forcing regular users to set something in

Summary of changes:
 sys/vm/vm_page.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

DragonFly BSD source repository

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