Allocating more RX descriptors that can fit in their related rings

[Kalle Valo]

Remi Pommarel <repk at triplefau.lt> writes:

> As far as I understand a bunch (ATH12K_RX_DESC_COUNT) of rx descriptors
> gets allocated, then CMEM is configured for those descriptors cookie
> conversion and is kept available in dp->rx_desc_free_list pool.
>
> Those descriptors seem to be used to fed two different rings, the
> rx_refill_buf_ring ring via ath12k_dp_rx_bufs_replenish() and the
> reo_reinject_ring one with ath12k_dp_rx_h_defrag_reo_reinject(). While
> the former is kept fully used if possible the latter is only used on
> demand (i.e. reinjection of defragmented MPDU).
>
> It seems that the number of RX descriptors ATH12K_RX_DESC_COUNT (12288)
> is higher than what those two rings can fit (DP_REO_REINJECT_RING_SIZE +
> DP_RXDMA_BUF_RING_SIZE = 4096 + 32 = 4128).
>
> My question is why are we allocating that much (12288) buffer if only a
> small part (4128) can be used in worst case ?
>
> Wouldn't it be ok to only allocate just enough RX descriptors to fill
> both ring (with proper 512 alignment to ease CMEM configuration) as
> below ?
>
>  #define ATH12K_RX_DESC_COUNT   ALIGN(DP_REO_REINJECT_RING_SIZE + \
>                                       DP_RXDMA_BUF_RING_SIZE, \
>                                       ATH12K_MAX_SPT_ENTRIES)
>
> Or am I missing something and this is going to impact performances ?

I don't know why it's so and no replies from others. I recommend just
sending a patch, preferably with numbers explaining how much memory is
saved, and let's see if anyone reacts.

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