On 2019-06-11, at 23:43:19 +0000, Matt Sickler wrote: > >-----Original Message----- > > From: Jeremy Sowden <jeremy@xxxxxxxxxx> > > I've had a go at getting the DMA AIO working. It compiles, but I > > don't have access to the hardware, so I have done no more testing > > than that. > > Honestly, it'd probably be better to just remove the AIO support > entirely. The one use case we had that could possibly have benefitted > from AIO has been switched away from DMA entirely. We switched > because the DMA buffer was a couple hundred bytes and the overhead of > setting up the DMA was killing throughput. AIO *might* have been able > to help there, but the userspace side of AIO is a PITA to work with. > IMO, if "AIO" for the kpc_dma driver were to make a come back, I think > it would be better to use something like io_uring The other things > that use DMA wouldn't benefit from AIO as they have to setup other > parts of the hardware that can't coordinate with the DMA controllers > (or at least not without a lot of work). > > TL;DR: it's probably better to just kill the AIO parts of the driver > than to try to make them work. > > >The fifth patch removes the cancel call-back because it is empty and > >so doesn't serve any purpose (AFAICS). However, it doesn't appear to > >be too tricky to implement something that would abort the transfer in > >the same manner that kpc_dma_close() if this would be useful. > > It's empty because I didn't have time to figure out how to cancel the > DMA operation on the hardware side. Doing the same "reset the whole > engine" type of cancel could work, but I'm not sure how well that > would mesh with aio_cancel (the latter would kill *all* in-flight > operations, the former is only killing the one). As I said above, > it's probably better to just remove all the AIO pieces. Righto. I'll take them out. J.
Attachment:
signature.asc
Description: PGP signature
_______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
