Re: [PATCH v2] net: mana: Use page pool fragments for RX buffers instead of full pages to improve memory efficiency.

[Jesper Dangaard Brouer <hawk@kernel.org>]

On 23/07/2025 21.07, Dipayaan Roy wrote:
> This patch enhances RX buffer handling in the mana driver by allocating
> pages from a page pool and slicing them into MTU-sized fragments, rather
> than dedicating a full page per packet. This approach is especially
> beneficial on systems with large page sizes like 64KB.
> 
> Key improvements:
> 
> - Proper integration of page pool for RX buffer allocations.
> - MTU-sized buffer slicing to improve memory utilization.
> - Reduce overall per Rx queue memory footprint.
> - Automatic fallback to full-page buffers when:
>     * Jumbo frames are enabled (MTU > PAGE_SIZE / 2).
>     * The XDP path is active, to avoid complexities with fragment reuse.
> - Removal of redundant pre-allocated RX buffers used in scenarios like MTU
>    changes, ensuring consistency in RX buffer allocation.
> 
> Testing on VMs with 64KB pages shows around 200% throughput improvement.
> Memory efficiency is significantly improved due to reduced wastage in page
> allocations. Example: We are now able to fit 35 rx buffers in a single 64kb
> page for MTU size of 1500, instead of 1 rx buffer per page previously.
> 
> Tested:
> 
> - iperf3, iperf2, and nttcp benchmarks.
> - Jumbo frames with MTU 9000.
> - Native XDP programs (XDP_PASS, XDP_DROP, XDP_TX, XDP_REDIRECT) for
>    testing the XDP path in driver.
> - Page leak detection (kmemleak).
> - Driver load/unload, reboot, and stress scenarios.

Chris (Cc) discovered a crash/bug[1] with page pool fragments used from 
the mlx5 driver.
He put together a BPF program that reproduces the issue here:
- [2] https://github.com/arges/xdp-redirector

Can I ask you to test that your driver against this reproducer?


[1] https://lore.kernel.org/all/aIEuZy6fUj_4wtQ6@861G6M3/

--Jesper