On 12/05/2015 03:17 AM, Christoph Hellwig wrote:
Hi Bart,
On Fri, Dec 04, 2015 at 03:08:15PM -0800, Bart Van Assche wrote:
While preparing this patch series I noticed that none of the SCSI RDMA
initiator drivers syncs RDMA buffers before performing RDMA. Does
anyone know why something like the code below is not present in these
drivers and why no dma_sync_sg operations are present in struct
ib_dma_mapping_ops ?
dma_map*/dma_unmap* have to do implicit syncs, so no explicit call
is required. That's probably the reason why we don't need them in
the weird RDMA shadows of these functions (for which I still don't
understand the reason, while we're at it..).
Hello Christoph,
struct ib_dma_mapping_ops was added through commit "IB: Add DMA mapping
functions to allow device drivers to interpose"
(https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=9b513090a3c5e4964f9ac09016c1586988abb3d5).
I'm not sure that these functions are still needed by the qib or ipath
drivers since the .dma_address and .dma_len members have been removed
some time ago from that structure (see also
http://thread.gmane.org/gmane.linux.drivers.rdma/19730). It would be
useful to have data available that shows the performance difference with
and without struct ib_dma_mapping_ops for the qib and ipath drivers but
I do not know whether such data is available publicly.
Bart.
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
