Hi Declan,

Please see inline.

Thanks,

Anoob


On 26-06-2018 15:42, Doherty, Declan wrote:

External Email

On 19/06/2018 7:26 AM, Anoob Joseph wrote:

quoted

Enabling crypto devs to specify the minimum headroom and tailroom it
expects in the mbuf. For net PMDs, standard headroom has to be honoured
by applications, which is not strictly followed for crypto devs. This

How is this done for NET PMDs, I don't see anything explicit in the
ehtdev API for specification of headroom requirements.

In rte_mbuf.h, the minimum size required for packets involved in rx/tx 
is specified and that considers headroom also. Applications usually use 
these default macros while creating mbufs which are involved in rx/tx.
https://git.dpdk.org/dpdk/tree/lib/librte_mbuf/rte_mbuf.h#n411

quoted

prevents crypto devs from using free space in mbuf (available as
head/tailroom) for internal requirements in crypto operations. Addition
of head/tailroom requirement will help PMDs to communicate such
requirements to the application.

The availability and use of head/tailroom is an optimization if the
hardware supports use of head/tailroom for crypto-op info. For devices
that do not support using the head/tailroom, they can continue to 
operate
without any performance-drop.

Is there any variations in requirements for terms headroom/tailroom on a
per algorithmic basis or is it purely for the device?

It is purely per device basis. The device can specify upper bounds for 
the head/tailroom. A device that even specified the room, may not even 
use the entire room in all cases. So it doesn't have to be algo specific.

quoted

Signed-off-by: Anoob Joseph <redacted>
---
  doc/guides/rel_notes/deprecation.rst | 4 ++++
  lib/librte_cryptodev/rte_cryptodev.h | 6 ++++++
  2 files changed, 10 insertions(+)

diff --git a/doc/guides/rel_notes/deprecation.rst 

b/doc/guides/rel_notes/deprecation.rst
index 1ce692e..a547289 100644

--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst

@@ -122,3 +122,7 @@ Deprecation Notices

    - Function ``rte_cryptodev_get_private_session_size()`` will be 
deprecated
      in 18.05, and it gets replaced with 
``rte_cryptodev_sym_get_private_session_size()``.
      It will be removed in 18.08.
+  - New field, ``min_headroom_req``, added in ``rte_cryptodev_info`` 
structure. It will be
+    added in 18.11.
+  - New field, ``min_tailroom_req``, added in ``rte_cryptodev_info`` 
structure. It will be
+    added in 18.11.

diff --git a/lib/librte_cryptodev/rte_cryptodev.h 

b/lib/librte_cryptodev/rte_cryptodev.h
index 92ce6d4..fa944b8 100644

--- a/lib/librte_cryptodev/rte_cryptodev.h
+++ b/lib/librte_cryptodev/rte_cryptodev.h

@@ -382,6 +382,12 @@ struct rte_cryptodev_info {

      unsigned max_nb_queue_pairs;
      /**< Maximum number of queues pairs supported by device. */

+     uint32_t min_headroom_req;
+     /**< Minimum mbuf headroom required by device */
+
+     uint32_t min_tailroom_req;
+     /**< Minimum mbuf tailroom required by device */
+
      struct {
              unsigned max_nb_sessions;
              /**< Maximum number of sessions supported by device. */