From: Stanislav Fomichev <stfomichev@gmail.com>
To: Wang Liang <wangliang74@huawei.com>
Cc: bjorn@kernel.org, magnus.karlsson@intel.com,
maciej.fijalkowski@intel.com, jonathan.lemon@gmail.com,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, horms@kernel.org, ast@kernel.org,
daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com,
yuehaibing@huawei.com, zhangchangzhong@huawei.com,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] xsk: correct tx_ring_empty_descs count statistics
Date: Mon, 31 Mar 2025 15:03:03 -0700 [thread overview]
Message-ID: <Z-sRF0G43HpGiGwH@mini-arch> (raw)
In-Reply-To: <Z-qzLyGKskaqgFh5@mini-arch>
On 03/31, Stanislav Fomichev wrote:
> On 03/29, Wang Liang wrote:
> > The tx_ring_empty_descs count may be incorrect, when set the XDP_TX_RING
> > option but do not reserve tx ring. Because xsk_poll() try to wakeup the
> > driver by calling xsk_generic_xmit() for non-zero-copy mode. So the
> > tx_ring_empty_descs count increases once the xsk_poll()is called:
> >
> > xsk_poll
> > xsk_generic_xmit
> > __xsk_generic_xmit
> > xskq_cons_peek_desc
> > xskq_cons_read_desc
> > q->queue_empty_descs++;
> >
> > To avoid this count error, add check for tx descs before send msg in poll.
> >
> > Fixes: df551058f7a3 ("xsk: Fix crash in poll when device does not support ndo_xsk_wakeup")
> > Signed-off-by: Wang Liang <wangliang74@huawei.com>
>
> Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Hmm, wait, I stumbled upon xskq_has_descs again and it looks only at
cached prod/cons. How is it supposed to work when the actual tx
descriptor is posted? Is there anything besides xskq_cons_peek_desc from
__xsk_generic_xmit that refreshes cached_prod?
next prev parent reply other threads:[~2025-03-31 22:03 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-29 6:15 [PATCH net] xsk: correct tx_ring_empty_descs count statistics Wang Liang
2025-03-31 15:22 ` Stanislav Fomichev
2025-03-31 22:03 ` Stanislav Fomichev [this message]
2025-04-01 2:35 ` Wang Liang
2025-04-01 6:57 ` Magnus Karlsson
2025-04-01 7:39 ` Wang Liang
2025-04-01 7:43 ` Wang Liang
2025-04-01 8:12 ` Magnus Karlsson
2025-04-01 9:33 ` Wang Liang
2025-04-01 11:00 ` Magnus Karlsson
2025-04-02 2:38 ` Wang Liang
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