Message-ID: <2d98cdcb-19c6-4a70-b8c6-b978b40663ee@samsung.com>
Date: Wed, 14 Aug 2024 11:17:35 +0200
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, mst@...hat.com, jasowang@...hat.com,
	xuanzhuo@...ux.alibaba.com, virtualization@...ts.linux.dev, ast@...nel.org,
	daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com,
	dave.taht@...il.com, kerneljasonxing@...il.com, hengqi@...ux.alibaba.com
Subject: Re: [PATCH net-next v3] virtio_net: add support for Byte Queue
 Limits

On 14.08.2024 09:49, Jiri Pirko wrote:
> Mon, Aug 12, 2024 at 06:55:26PM CEST, m.szyprowski@...sung.com wrote:
>> On 12.08.2024 18:47, Jiri Pirko wrote:
>>> Mon, Aug 12, 2024 at 04:57:24PM CEST, m.szyprowski@...sung.com wrote:
>>>> On 18.06.2024 16:44, Jiri Pirko wrote:
>>>>> From: Jiri Pirko <jiri@...dia.com>
>>>>>
>>>>> 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@...dia.com>
>>>>> ---
>>>>> 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@...get:~# 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.
> I found the problem. Following patch will help:
>
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 3f10c72743e9..c6af18948092 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2867,8 +2867,8 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
>   	if (err < 0)
>   		goto err_xdp_reg_mem_model;
>   
> -	virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
>   	netdev_tx_reset_queue(netdev_get_tx_queue(vi->dev, qp_index));
> +	virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
>   	virtnet_napi_tx_enable(vi, vi->sq[qp_index].vq, &vi->sq[qp_index].napi);
>   
>   	return 0;
>
>
> Will submit the patch in a jiff. Thanks!

Confirmed. The above change fixed this issue in my tests.

Feel free to add:

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Powered by blists - more mailing lists