Reclaiming memory for network interface

[Sujeev Dias <sdias@codeaurora.org>]

Hi

Setup: sdm845 connected to external modem over pcie interface

During a data call, we found out we spend more than 25% of cpu for 
memory ops with io coherency.  That include allocation, freeing, dma 
mapping, and unmapping.  As we pushing to higher data rate (beyond 7 
Gbps), the time we spend in memory operation is significant. So, we're 
looking into ways we can reclaim this memory.

One of idea we're thinking is:

1. allocate pages

2. Increment reference count of page

3. allocate skb, and assign page into paged data portion

4. Assign cb function to skb->destructor

5. once destructor get called, move the page to a new skb


Sound simple enough, but we couldn't find anyone actually doing this 
way.  Anything to be concern with above proposal? We see some example of 
using destructor to do deferred unmap but didn't see any example of 
re-using the buffer. Also, couldn't find any meaningful discussion about 
reclaiming memory for network data. Any thoughts on how we should solve 
this issue?  Any comment is welcome, thanks.


Sincerely

Sujeev


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