From: hawk@kernel•org
To: netdev@vger•kernel.org
Cc: hawk@kernel•org, kernel-team@cloudflare•com,
"Jonas Köppeler" <j.koeppeler@tu-berlin•de>,
"Andrew Lunn" <andrew+netdev@lunn•ch>,
"David S. Miller" <davem@davemloft•net>,
"Eric Dumazet" <edumazet@google•com>,
"Jakub Kicinski" <kuba@kernel•org>,
"Paolo Abeni" <pabeni@redhat•com>,
"Simon Horman" <horms@kernel•org>,
"Jonathan Corbet" <corbet@lwn•net>,
"Shuah Khan" <skhan@linuxfoundation•org>,
"Kuniyuki Iwashima" <kuniyu@google•com>,
"Stanislav Fomichev" <sdf@fomichev•me>,
"Christian Brauner" <brauner@kernel•org>,
"Yury Norov" <ynorov@nvidia•com>,
"Krishna Kumar" <krikku@gmail•com>,
"Yajun Deng" <yajun.deng@linux•dev>,
linux-doc@vger•kernel.org, linux-kernel@vger•kernel.org
Subject: [PATCH net-next v5 2/5] net: add dev->bql flag to allow BQL sysfs for IFF_NO_QUEUE devices
Date: Tue, 5 May 2026 15:21:54 +0200 [thread overview]
Message-ID: <20260505132159.241305-3-hawk@kernel.org> (raw)
In-Reply-To: <20260505132159.241305-1-hawk@kernel.org>
From: Jesper Dangaard Brouer <hawk@kernel•org>
Virtual devices with IFF_NO_QUEUE or lltx are excluded from BQL sysfs
by netdev_uses_bql(), since they traditionally lack real hardware
queues. However, some virtual devices like veth implement a real
ptr_ring FIFO with NAPI processing and benefit from BQL to limit
in-flight bytes and reduce latency.
Add a per-device 'bql' bitfield boolean in the priv_flags_slow section
of struct net_device. When set, it overrides the IFF_NO_QUEUE/lltx
exclusion and exposes BQL sysfs entries (/sys/class/net/<dev>/queues/
tx-<n>/byte_queue_limits/). The flag is still gated on CONFIG_BQL.
This allows drivers that use BQL despite being IFF_NO_QUEUE to opt in
to sysfs visibility for monitoring and debugging.
Signed-off-by: Jesper Dangaard Brouer <hawk@kernel•org>
Tested-by: Jonas Köppeler <j.koeppeler@tu-berlin•de>
---
Documentation/networking/net_cachelines/net_device.rst | 1 +
include/linux/netdevice.h | 2 ++
net/core/net-sysfs.c | 8 +++++++-
3 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
index 1c19bb7705df..b775d3235a2d 100644
--- a/Documentation/networking/net_cachelines/net_device.rst
+++ b/Documentation/networking/net_cachelines/net_device.rst
@@ -170,6 +170,7 @@ unsigned_long:1 see_all_hwtstamp_requests
unsigned_long:1 change_proto_down
unsigned_long:1 netns_immutable
unsigned_long:1 fcoe_mtu
+unsigned_long:1 bql netdev_uses_bql(net-sysfs.c)
struct list_head net_notifier_list
struct macsec_ops* macsec_ops
struct udp_tunnel_nic_info* udp_tunnel_nic_info
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 744ffa243501..d4c7b020b6a7 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2065,6 +2065,7 @@ enum netdev_reg_state {
* @change_proto_down: device supports setting carrier via IFLA_PROTO_DOWN
* @netns_immutable: interface can't change network namespaces
* @fcoe_mtu: device supports maximum FCoE MTU, 2158 bytes
+ * @bql: device uses BQL (DQL sysfs) despite having IFF_NO_QUEUE
*
* @net_notifier_list: List of per-net netdev notifier block
* that follow this device when it is moved
@@ -2479,6 +2480,7 @@ struct net_device {
unsigned long change_proto_down:1;
unsigned long netns_immutable:1;
unsigned long fcoe_mtu:1;
+ unsigned long bql:1;
struct list_head net_notifier_list;
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 3318b5666e43..82833e5dae03 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1945,10 +1945,16 @@ static const struct kobj_type netdev_queue_ktype = {
static bool netdev_uses_bql(const struct net_device *dev)
{
+ if (!IS_ENABLED(CONFIG_BQL))
+ return false;
+
+ if (dev->bql)
+ return true;
+
if (dev->lltx || (dev->priv_flags & IFF_NO_QUEUE))
return false;
- return IS_ENABLED(CONFIG_BQL);
+ return true;
}
static int netdev_queue_add_kobject(struct net_device *dev, int index)
--
2.43.0
next prev parent reply other threads:[~2026-05-05 13:22 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-05 13:21 [PATCH net-next v5 0/5] veth: add Byte Queue Limits (BQL) support hawk
2026-05-05 13:21 ` [PATCH net-next v5 1/5] veth: fix OOB txq access in veth_poll() with asymmetric queue counts hawk
2026-05-07 14:25 ` Paolo Abeni
2026-05-05 13:21 ` hawk [this message]
2026-05-05 13:21 ` [PATCH net-next v5 3/5] veth: implement Byte Queue Limits (BQL) for latency reduction hawk
2026-05-07 6:54 ` Simon Schippers
2026-05-07 13:21 ` Paolo Abeni
2026-05-07 14:34 ` Paolo Abeni
2026-05-07 14:46 ` Simon Schippers
2026-05-07 19:09 ` Jesper Dangaard Brouer
2026-05-07 20:12 ` Simon Schippers
2026-05-07 20:45 ` Jesper Dangaard Brouer
2026-05-08 8:01 ` Simon Schippers
2026-05-08 9:20 ` Simon Schippers
2026-05-09 2:06 ` Jakub Kicinski
2026-05-09 9:09 ` Jesper Dangaard Brouer
2026-05-10 15:56 ` Jakub Kicinski
2026-05-11 8:11 ` Jesper Dangaard Brouer
2026-05-11 9:55 ` Simon Schippers
2026-05-11 18:08 ` Jesper Dangaard Brouer
2026-05-11 20:37 ` Simon Schippers
2026-05-12 13:54 ` Jesper Dangaard Brouer
2026-05-12 21:55 ` Simon Schippers
2026-05-19 20:51 ` Simon Schippers
2026-05-22 7:17 ` Jonas Köppeler
[not found] ` <4ae9400a-8919-4ffc-8db3-0c334e2aa462@tu-berlin.de>
2026-05-22 8:41 ` Simon Schippers
2026-05-22 16:26 ` Jonas Köppeler
2026-05-23 16:09 ` Simon Schippers
2026-05-26 9:54 ` Jonas Köppeler
2026-05-26 14:35 ` Simon Schippers
2026-05-26 14:55 ` Jonas Köppeler
2026-05-26 15:07 ` Simon Schippers
2026-05-27 7:38 ` Jesper Dangaard Brouer
2026-05-27 7:59 ` Simon Schippers
2026-05-27 8:38 ` Simon Schippers
2026-05-05 13:21 ` [PATCH net-next v5 4/5] veth: add tx_timeout watchdog as BQL safety net hawk
2026-05-05 13:21 ` [PATCH net-next v5 5/5] net: sched: add timeout count to NETDEV WATCHDOG message hawk
2026-05-07 14:30 ` [PATCH net-next v5 0/5] veth: add Byte Queue Limits (BQL) support patchwork-bot+netdevbpf
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