On Mon, Feb 06, 2017 at 01:46:09PM +0200, Leon Romanovsky wrote: > On Mon, Feb 06, 2017 at 10:56:56AM +0000, Amrani, Ram wrote: > > > This patchset from Leon adds direct access to mlx5 devices. > > > > > > The libibverbs API is an abstract API. It is agnostic to any underlying > > > provider specific implementation. While this abstraction has the advantage of > > > user applications portability it has a performance penalty. For some > > > applications optimizing performance is more important than portability. > > > > > > The mlx5 direct verbs API introduced in this patchset is intended for such > > > applications. It exposes mlx5 specific low level data path > > > (send/receive/completion) operations, allowing the application to bypass the > > > libibverbs data path API. > > > > > > The proposed interface consists from small number of hardware specific headers > > > with relevant inline functions and conversion logic from ibverbs structures to > > > mlx5 related structures. > > > > > While I'm always for better performance, I'm not sure driver specific APIs is the way. > > This will hurt portability for users. > > As it was expressed in cover letter, this feature is intended for > users who want performance and understand the disadvantages of such > direct approach. To expound on that - the trade off we discussed in-person was we either do something like this or continually take endless vendor-specific patches to add 'common' core code for unstandardized chip-specific features. This seemed like the least bad trade off, if another vendor wants the same things then they could work together and make an actual multi-chip common API. I was expecting this interface to be used in only a few places, like the next level of middleware libraries (libfabric, mxm, etc) not for many end-users. I'm still not completely sure what this API is intended to do, if it is really just performance then I am less supportive and would rather see an approach like libfabric where a user can build a single provider verbs with the same source API, but optimized.... Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
