netdev - Re: [PATCH net] bnxt_en: update xdp_rxq

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Message-ID: <74fcb647-0226-4aa4-bf99-06fee8d510d0@davidwei.uk>
Date: Fri, 19 Jul 2024 22:12:59 -0700
From: David Wei <dw@...idwei.uk>
To: Taehee Yoo <ap420073@...il.com>, davem@...emloft.net, kuba@...nel.org,
 pabeni@...hat.com, edumazet@...gle.com, michael.chan@...adcom.com,
 netdev@...r.kernel.org
Cc: somnath.kotur@...adcom.com, horms@...nel.org
Subject: Re: [PATCH net] bnxt_en: update xdp_rxq_info in queue restart logic

On 2024-07-18 21:19, Taehee Yoo wrote:
> When the netdev_rx_queue_restart() restarts queues, the bnxt_en driver
> updates(creates and deletes) a page_pool.
> But it doesn't update xdp_rxq_info, so the xdp_rxq_info is still
> connected to an old page_pool.
> So, bnxt_rx_ring_info->page_pool indicates a new page_pool, but
> bnxt_rx_ring_info->xdp_rxq is still connected to an old page_pool.
> 
> An old page_pool is no longer used so it is supposed to be
> deleted by page_pool_destroy() but it isn't.
> Because the xdp_rxq_info is holding the reference count for it and the
> xdp_rxq_info is not updated, an old page_pool will not be deleted in
> the queue restart logic.
> 
> Before restarting 1 queue:
> ./tools/net/ynl/samples/page-pool
> enp10s0f1np1[6] page pools: 4 (zombies: 0)
> 	refs: 8192 bytes: 33554432 (refs: 0 bytes: 0)
> 	recycling: 0.0% (alloc: 128:8048 recycle: 0:0)
> 
> After restarting 1 queue:
> ./tools/net/ynl/samples/page-pool
> enp10s0f1np1[6] page pools: 5 (zombies: 0)
> 	refs: 10240 bytes: 41943040 (refs: 0 bytes: 0)
> 	recycling: 20.0% (alloc: 160:10080 recycle: 1920:128)

Thanks, didn't know this existed! As a follow up once Mina lands his
devmem TCP series with netdev_rx_queue_restart(), a netdev netlink
selftest using would be great.

> 
> Before restarting queues, an interface has 4 page_pools.
> After restarting one queue, an interface has 5 page_pools, but it
> should be 4, not 5.
> The reason is that queue restarting logic creates a new page_pool and
> an old page_pool is not deleted due to the absence of an update of
> xdp_rxq_info logic.
> 
> Fixes: 2d694c27d32e ("bnxt_en: implement netdev_queue_mgmt_ops")
> Signed-off-by: Taehee Yoo <ap420073@...il.com>
> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index bb3be33c1bbd..11d8459376a9 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
[...]
> @@ -15065,6 +15079,8 @@ static void bnxt_queue_mem_free(struct net_device *dev, void *qmem)
>  	page_pool_destroy(rxr->page_pool);
>  	rxr->page_pool = NULL;
>  
> +	xdp_rxq_info_unreg(&rxr->xdp_rxq);
> +

IMO this should go before page_pool_destroy() for symmetry with
bnxt_free_rx_rings(). I know there's already a call deep inside of
xdp_rxq_info_unreg().

>  	ring = &rxr->rx_ring_struct;
>  	bnxt_free_ring(bp, &ring->ring_mem);
>  
> @@ -15145,6 +15161,7 @@ static int bnxt_queue_start(struct net_device *dev, void *qmem, int idx)
>  	rxr->rx_sw_agg_prod = clone->rx_sw_agg_prod;
>  	rxr->rx_next_cons = clone->rx_next_cons;
>  	rxr->page_pool = clone->page_pool;
> +	memcpy(&rxr->xdp_rxq, &clone->xdp_rxq, sizeof(struct xdp_rxq_info));

Assignment is fine here.