Am 10.07.24 um 16:35 schrieb Lei Liu:
在 2024/7/10 22:14, Christian König 写道:
Am 10.07.24 um 15:57 schrieb Lei Liu:
Use vm_insert_page to establish a mapping for the memory allocated
by dmabuf, thus supporting direct I/O read and write; and fix the
issue of incorrect memory statistics after mapping dmabuf memory.
Well big NAK to that! Direct I/O is intentionally disabled on DMA-bufs.
Hello! Could you explain why direct_io is disabled on DMABUF? Is there
any historical reason for this?
It's basically one of the most fundamental design decision of DMA-Buf.
The attachment/map/fence model DMA-buf uses is not really compatible
with direct I/O on the underlying pages.
We already discussed enforcing that in the DMA-buf framework and this
patch probably means that we should really do that.
Regards,
Christian.
Thank you for your response. With the application of AI large model
edgeification, we urgently need support for direct_io on DMABUF to
read some very large files. Do you have any new solutions or plans for
this?
We have seen similar projects over the years and all of those turned out
to be complete shipwrecks.
There is currently a patch set under discussion to give the network
subsystem DMA-buf support. If you are interest in network direct I/O
that could help.
Additional to that a lot of GPU drivers support userptr usages, e.g. to
import malloced memory into the GPU driver. You can then also do direct
I/O on that malloced memory and the kernel will enforce correct handling
with the GPU driver through MMU notifiers.
But as far as I know a general DMA-buf based solution isn't possible.
Regards,
Christian.
Regards,
Lei Liu.
Lei Liu (2):
mm: dmabuf_direct_io: Support direct_io for memory allocated by
dmabuf
mm: dmabuf_direct_io: Fix memory statistics error for dmabuf
allocated
memory with direct_io support
drivers/dma-buf/heaps/system_heap.c | 5 +++--
fs/proc/task_mmu.c | 8 +++++++-
include/linux/mm.h | 1 +
mm/memory.c | 15 ++++++++++-----
mm/rmap.c | 9 +++++----
5 files changed, 26 insertions(+), 12 deletions(-)
