On 12.08.2024 18:47, Jiri Pirko wrote:
> Mon, Aug 12, 2024 at 04:57:24PM CEST, m.szyprowski@xxxxxxxxxxx wrote:
>> On 18.06.2024 16:44, Jiri Pirko wrote:
>>> From: Jiri Pirko <jiri@xxxxxxxxxx>
>>>
>>> Add support for Byte Queue Limits (BQL).
>>>
>>> Tested on qemu emulated virtio_net device with 1, 2 and 4 queues.
>>> Tested with fq_codel and pfifo_fast. Super netperf with 50 threads is
>>> running in background. Netperf TCP_RR results:
>>>
>>> NOBQL FQC 1q: 159.56 159.33 158.50 154.31 agv: 157.925
>>> NOBQL FQC 2q: 184.64 184.96 174.73 174.15 agv: 179.62
>>> NOBQL FQC 4q: 994.46 441.96 416.50 499.56 agv: 588.12
>>> NOBQL PFF 1q: 148.68 148.92 145.95 149.48 agv: 148.2575
>>> NOBQL PFF 2q: 171.86 171.20 170.42 169.42 agv: 170.725
>>> NOBQL PFF 4q: 1505.23 1137.23 2488.70 3507.99 agv: 2159.7875
>>> BQL FQC 1q: 1332.80 1297.97 1351.41 1147.57 agv: 1282.4375
>>> BQL FQC 2q: 768.30 817.72 864.43 974.40 agv: 856.2125
>>> BQL FQC 4q: 945.66 942.68 878.51 822.82 agv: 897.4175
>>> BQL PFF 1q: 149.69 151.49 149.40 147.47 agv: 149.5125
>>> BQL PFF 2q: 2059.32 798.74 1844.12 381.80 agv: 1270.995
>>> BQL PFF 4q: 1871.98 4420.02 4916.59 13268.16 agv: 6119.1875
>>>
>>> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx>
>>> ---
>>> v2->v3:
>>> - fixed the switch from/to orphan mode while skbs are yet to be
>>> completed by using the second least significant bit in virtqueue
>>> token pointer to indicate skb is orphan. Don't account orphan
>>> skbs in completion.
>>> - reorganized parallel skb/xdp free stats accounting to napi/others.
>>> - fixed kick condition check in orphan mode
>>> v1->v2:
>>> - moved netdev_tx_completed_queue() call into __free_old_xmit(),
>>> propagate use_napi flag to __free_old_xmit() and only call
>>> netdev_tx_completed_queue() in case it is true
>>> - added forgotten call to netdev_tx_reset_queue()
>>> - fixed stats for xdp packets
>>> - fixed bql accounting when __free_old_xmit() is called from xdp path
>>> - handle the !use_napi case in start_xmit() kick section
>>> ---
>>> drivers/net/virtio_net.c | 81 ++++++++++++++++++++++++++++------------
>>> 1 file changed, 57 insertions(+), 24 deletions(-)
>> I've recently found an issue with virtio-net driver and system
>> suspend/resume. Bisecting pointed to the c8bd1f7f3e61 ("virtio_net: add
>> support for Byte Queue Limits") commit and this patch. Once it got
>> merged to linux-next and then Linus trees, the driver occasionally
>> crashes with the following log (captured on QEMU's ARM 32bit 'virt'
>> machine):
>>
>> root@target:~# time rtcwake -s10 -mmem
>> rtcwake: wakeup from "mem" using /dev/rtc0 at Sat Aug 10 12:40:26 2024
>> PM: suspend entry (s2idle)
>> Filesystems sync: 0.000 seconds
>> Freezing user space processes
>> Freezing user space processes completed (elapsed 0.006 seconds)
>> OOM killer disabled.
>> Freezing remaining freezable tasks
>> Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
>> ------------[ cut here ]------------
>> kernel BUG at lib/dynamic_queue_limits.c:99!
>> Internal error: Oops - BUG: 0 [#1] SMP ARM
>> Modules linked in: bluetooth ecdh_generic ecc libaes
>> CPU: 1 PID: 1282 Comm: rtcwake Not tainted
>> 6.10.0-rc3-00732-gc8bd1f7f3e61 #15240
>> Hardware name: Generic DT based system
>> PC is at dql_completed+0x270/0x2cc
>> LR is at __free_old_xmit+0x120/0x198
>> pc : [<c07ffa54>] lr : [<c0c42bf4>] psr: 80000013
>> ...
>> Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
>> Control: 10c5387d Table: 43a4406a DAC: 00000051
>> ...
>> Process rtcwake (pid: 1282, stack limit = 0xfbc21278)
>> Stack: (0xe0805e80 to 0xe0806000)
>> ...
>> Call trace:
>> dql_completed from __free_old_xmit+0x120/0x198
>> __free_old_xmit from free_old_xmit+0x44/0xe4
>> free_old_xmit from virtnet_poll_tx+0x88/0x1b4
>> virtnet_poll_tx from __napi_poll+0x2c/0x1d4
>> __napi_poll from net_rx_action+0x140/0x2b4
>> net_rx_action from handle_softirqs+0x11c/0x350
>> handle_softirqs from call_with_stack+0x18/0x20
>> call_with_stack from do_softirq+0x48/0x50
>> do_softirq from __local_bh_enable_ip+0xa0/0xa4
>> __local_bh_enable_ip from virtnet_open+0xd4/0x21c
>> virtnet_open from virtnet_restore+0x94/0x120
>> virtnet_restore from virtio_device_restore+0x110/0x1f4
>> virtio_device_restore from dpm_run_callback+0x3c/0x100
>> dpm_run_callback from device_resume+0x12c/0x2a8
>> device_resume from dpm_resume+0x12c/0x1e0
>> dpm_resume from dpm_resume_end+0xc/0x18
>> dpm_resume_end from suspend_devices_and_enter+0x1f0/0x72c
>> suspend_devices_and_enter from pm_suspend+0x270/0x2a0
>> pm_suspend from state_store+0x68/0xc8
>> state_store from kernfs_fop_write_iter+0x10c/0x1cc
>> kernfs_fop_write_iter from vfs_write+0x2b0/0x3dc
>> vfs_write from ksys_write+0x5c/0xd4
>> ksys_write from ret_fast_syscall+0x0/0x54
>> Exception stack(0xe8bf1fa8 to 0xe8bf1ff0)
>> ...
>> ---[ end trace 0000000000000000 ]---
>> Kernel panic - not syncing: Fatal exception in interrupt
>> ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
>>
>> I have fully reproducible setup for this issue. Reverting it together
>> with f8321fa75102 ("virtio_net: Fix napi_skb_cache_put warning") (due to
>> some code dependencies) fixes this issue on top of Linux v6.11-rc1 and
>> recent linux-next releases. Let me know if I can help debugging this
>> issue further and help fixing.
> Will fix this tomorrow. In the meantime, could you provide full
> reproduce steps?
Well, it is easy to reproduce it simply by calling
# time rtcwake -s10 -mmem
a few times and sooner or later it will cause a kernel panic.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
