> From: Hanumanth Pothula [mailto:hpoth...@marvell.com] > Sent: Friday, 12 August 2022 12.47 > > Presently, the 'Buffer Split' feature supports sending multiple > segments of the received packet to PMD, which programs the HW > to receive the packet in segments from different pools. > > This patch extends the feature to support the pool sort capability. > Some of the HW has support for choosing memory pools based on the > packet's size. The pool sort capability allows PMD to choose a > memory pool based on the packet's length. > > This is often useful for saving the memory where the application > can create a different pool to steer the specific size of the > packet, thus enabling effective use of memory. > > For example, let's say HW has a capability of three pools, > - pool-1 size is 2K > - pool-2 size is > 2K and < 4K > - pool-3 size is > 4K > Here, > pool-1 can accommodate packets with sizes < 2K > pool-2 can accommodate packets with sizes > 2K and < 4K > pool-3 can accommodate packets with sizes > 4K > > With pool sort capability enabled in SW, an application may create > three pools of different sizes and send them to PMD. Allowing PMD > to program HW based on packet lengths. So that packets with less > than 2K are received on pool-1, packets with lengths between 2K > and 4K are received on pool-2 and finally packets greater than 4K > are received on pool-3. > > The following two capabilities are added to the rte_eth_rxseg_capa > structure, > 1. pool_sort --> tells pool sort capability is supported by HW. > 2. max_npool --> max number of pools supported by HW. > > Defined new structure rte_eth_rxseg_sort, to be used only when pool > sort capability is present. If required this may be extended further > to support more configurations. > > Signed-off-by: Hanumanth Pothula <hpoth...@marvell.com> > Change-Id: I5a2485a7919616902c468c767b5c01834d4a2c27 > ---
I like the concept of a PMD being able to use different mbuf pools depending on packet size. However, the "pool sort" feature is not an extension of the "buffer split" feature, but a separate feature. The API and documentation must reflect this. Please also consider this, when you implement it in the drivers: If no buffers are available in one of the pools, the next (larger) pool should be used instead of dropping the packet. Here's another example use case: Assuming that 25 % of internet traffic is tiny packets (e.g. empty TCP ACK packets), a separate pool for those could be used.
