[dpdk-dev] [PATCH] Scheduler: add driver for scheduler crypto pmd

[Neil Horman]

On Fri, Dec 02, 2016 at 04:22:16PM +0000, Declan Doherty wrote:
> On 02/12/16 14:57, Bruce Richardson wrote:
> > On Fri, Dec 02, 2016 at 03:31:24PM +0100, Thomas Monjalon wrote:
> > > 2016-12-02 14:15, Fan Zhang:
> > > > This patch provides the initial implementation of the scheduler poll mode
> > > > driver using DPDK cryptodev framework.
> > > > 
> > > > Scheduler PMD is used to schedule and enqueue the crypto ops to the
> > > > hardware and/or software crypto devices attached to it (slaves). The
> > > > dequeue operation from the slave(s), and the possible dequeued crypto op
> > > > reordering, are then carried out by the scheduler.
> > > > 
> > > > The scheduler PMD can be used to fill the throughput gap between the
> > > > physical core and the existing cryptodevs to increase the overall
> > > > performance. For example, if a physical core has higher crypto op
> > > > processing rate than a cryptodev, the scheduler PMD can be introduced to
> > > > attach more than one cryptodevs.
> > > > 
> > > > This initial implementation is limited to supporting the following
> > > > scheduling modes:
> > > > 
> > > > - CRYPTO_SCHED_SW_ROUND_ROBIN_MODE (round robin amongst attached software
> > > >     slave cryptodevs, to set this mode, the scheduler should have been
> > > >     attached 1 or more software cryptodevs.
> > > > 
> > > > - CRYPTO_SCHED_HW_ROUND_ROBIN_MODE (round robin amongst attached hardware
> > > >     slave cryptodevs (QAT), to set this mode, the scheduler should have
> > > >     been attached 1 or more QATs.
> > > 
> > > Could it be implemented on top of the eventdev API?
> > > 
> > Not really. The eventdev API is for different types of scheduling
> > between multiple sources that are all polling for packets, compared to
> > this, which is more analgous - as I understand it - to the bonding PMD
> > for ethdev.
> > 
> > To make something like this work with an eventdev API you would need to
> > use one of the following models:
> > * have worker cores for offloading packets to the different crypto
> >   blocks pulling from the eventdev APIs. This would make it difficult to
> >   do any "smart" scheduling of crypto operations between the blocks,
> >   e.g. that one crypto instance may be better at certain types of
> >   operations than another.
> > * move the logic in this driver into an existing eventdev instance,
> >   which uses the eventdev api rather than the crypto APIs and so has an
> >   extra level of "structure abstraction" that has to be worked though.
> >   It's just not really a good fit.
> > 
> > So for this workload, I believe the pseudo-cryptodev instance is the
> > best way to go.
> > 
> > /Bruce
> > 
> 
> 
> As Bruce says this is much more analogous to the ethdev bonding driver, the
> main idea is to allow different crypto op scheduling mechanisms to be
> defined transparently to an application. This could be load-balancing across
> multiple hw crypto devices, or having a software crypto device to act as a
> backup device for a hw accelerator if it becomes oversubscribed. I think the
> main advantage of a crypto-scheduler approach means that the data path of
> the application doesn't need to have any knowledge that scheduling is
> happening at all, it is just using a different crypto device id, which is
> then manages the distribution of crypto work.
> 
> 
> 
This is a good deal like the bonding pmd, and so from a certain standpoint it
makes sense to do this, but whereas the bonding pmd is meant to create a single
path to a logical network over several physical networks, this pmd really only
focuses on maximizing througput, and for that we already have tools.  As Thomas
mentions, there is the eventdev library, but from my view the distributor
library already fits this bill.  It already is a basic framework to process
mbufs in parallel according to whatever policy you want to implement, which
sounds like exactly what the goal of this pmd is.  

Neil