[dpdk-dev] [RFC PATCH 0/3] *** SUBJECT HERE ***

[Ananyev, Konstantin]

Oops sorry, resending with proper subject.

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Friday, December 1, 2017 2:48 PM
> To: dev at dpdk.org; dev at dpdk.org
> Cc: Ananyev, Konstantin <konstantin.ananyev at intel.com>
> Subject: [RFC PATCH 0/3] *** SUBJECT HERE ***
> 
> The series introduces 2 main changes:
> 
> 1.Introduce a separate data structure (rte_eth_queue_local)
> to store local to given process (i.e. no-shareable) information
> for each configured rx/tx queue.
> Memory for that structure is allocated/freed dynamically during
> rte_eth_dev_configure().
> Reserve a space for queue specific (rx|tx)_pkt_burst(),
> tx_pkt_prepare() function pointers inside that structure.
> Move rx/tx callback related information inside that structure.
> That introduces a change in current behavior: all callbacks for
> un-configured queues will be automatically removed.
> Also as size of struct rte_eth_dev changes that patch is an ABI breakage,
> so deprecation notice for 18.05 is filled.
> Further suggestions how to introduce the same functionality
> without ABI breakage are welcome.
> 
> 2. Make it safe to remove rx/tx callback at runtime.
> Right now it is not possible for the application to figure out
> when it is safe to free removed callback handle and
> associated with it resources(unless the queue is stopped).
> That's probably not a big problem if all callbacks are static
> hange through whole application lifetime)
> and/or application doesn't allocate any resources for the callback handler.
> Though if callbacks have to be added/removed dynamically and
> callback handler would require more resources to operate properly -
> then it might become an issue.
> So patch #2 fixes that problem - now as soon as
> rte_eth_remove_(rx|tx)_callback() completes successfully, application
> can safely free all associated with the removed callback resources.
> 
> Performance impact:
> If application doesn't use RX/TX callbacks, then the tests I run didn't
> reveal any performance degradation.
> Though if application do use RX/TX callbacks - patch #2 does introduce
> some slowdown.
> 
> To be more specific here, on BDW (E5-2699 v4) 2.2GHz, 4x10Gb (X520-4)
> with http://dpdk.org/dev/patchwork/patch/31864/ patch installed I got:
> 1) testpmd ... --latencystats=1 - slowdown < 1%
> 2) examples//l3fwd ... --parse-ptype - - slowdown < 1%
> 3) examples/rxtx_callbacks - slowdown ~8%
> All that in terms of packet throughput (Mpps).
> 
> Ability to safely remove callbacks at runtime implies
> some sort of synchronization.
> Even I tried to make it as light as possible,
> probably some slowdown is unavoidable.
> Of course instead of introducing these changes at rte_ethdev layer
> similar technique could be applied on individual callback basis.
> In that case it would be up to callback writer/installer to decide
> does he/she need a removable at runtime callback or not.
> Though in that case, each installed callback might introduce extra
> synchronization overhead and slowdown.
> 
> Konstantin Ananyev (3):
>   ethdev: introduce eth_queue_local
>   ethdev: make it safe to remove rx/tx callback at runtime
>   doc: ethdev ABI change deprecation notice
> 
>  doc/guides/rel_notes/deprecation.rst |   5 +
>  lib/librte_ether/rte_ethdev.c        | 390 ++++++++++++++++++++++-------------
>  lib/librte_ether/rte_ethdev.h        | 174 ++++++++++++----
>  3 files changed, 387 insertions(+), 182 deletions(-)
> 
> --
> 2.13.5