netdev - Re: [BUG] mlx5_core memory management issue

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Message-ID: <aJzfPFCTlc35b2Bp@861G6M3>
Date: Wed, 13 Aug 2025 13:53:48 -0500
From: Chris Arges <carges@...udflare.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: Jesse Brandeburg <jbrandeburg@...udflare.com>, netdev@...r.kernel.org,
	bpf@...r.kernel.org, kernel-team <kernel-team@...udflare.com>,
	Jesper Dangaard Brouer <hawk@...nel.org>, tariqt@...dia.com,
	saeedm@...dia.com, Leon Romanovsky <leon@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Simon Horman <horms@...nel.org>,
	Andrew Rzeznik <arzeznik@...udflare.com>,
	Yan Zhai <yan@...udflare.com>
Subject: Re: [BUG] mlx5_core memory management issue

On 2025-08-12 16:25:58, Chris Arges wrote:
> On 2025-08-12 20:19:30, Dragos Tatulea wrote:
> > On Tue, Aug 12, 2025 at 11:55:39AM -0700, Jesse Brandeburg wrote:
> > > On 8/12/25 8:44 AM, 'Dragos Tatulea' via kernel-team wrote:
> > > 
> > > > diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> > > > index 482d284a1553..484216c7454d 100644
> > > > --- a/kernel/bpf/devmap.c
> > > > +++ b/kernel/bpf/devmap.c
> > > > @@ -408,8 +408,10 @@ static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
> > > >          /* If not all frames have been transmitted, it is our
> > > >           * responsibility to free them
> > > >           */
> > > > +       xdp_set_return_frame_no_direct();
> > > >          for (i = sent; unlikely(i < to_send); i++)
> > > >                  xdp_return_frame_rx_napi(bq->q[i]);
> > > > +       xdp_clear_return_frame_no_direct();
> > > 
> > > Why can't this instead just be xdp_return_frame(bq->q[i]); with no
> > > "no_direct" fussing?
> > > 
> > > Wouldn't this be the safest way for this function to call frame completion?
> > > It seems like presuming the calling context is napi is wrong?
> > >
> > It would be better indeed. Thanks for removing my horse glasses!
> > 
> > Once Chris verifies that this works for him I can prepare a fix patch.
> >
> Working on that now, I'm testing a kernel with the following change:
> 
> ---
> 
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index 3aa002a47..ef86d9e06 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -409,7 +409,7 @@ static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
>          * responsibility to free them
>          */
>         for (i = sent; unlikely(i < to_send); i++)
> -               xdp_return_frame_rx_napi(bq->q[i]);
> +               xdp_return_frame(bq->q[i]);
>  
>  out:
>         bq->count = 0;

This patch resolves the issue I was seeing and I am no longer able to
reproduce the issue. I tested for about 2 hours, when the reproducer usually
takes about 1-2 minutes.

--chris