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Message-ID: <ZrxoC_jCc00MzD-o@nanopsycho.orion>
Date: Wed, 14 Aug 2024 10:17:15 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Marek Szyprowski <m.szyprowski@...sung.com>
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
Wed, Aug 14, 2024 at 09:49:57AM CEST, jiri@...nulli.us 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);
Hmm, I have to look at this a bit more. I think this might be accidental
fix. The thing is, napi can be triggered even if it is disabled:
->__local_bh_enable_ip()
-> net_rx_action()
-> __napi_poll()
Here __napi_poll() calls napi_is_scheduled() and calls virtnet_poll_tx()
in case napi is scheduled. napi_is_scheduled() checks NAPI_STATE_SCHED
bit in napi state.
However, this bit is set previously by netif_napi_add_weight().
>
> > ...
>
>Best regards
>--
>Marek Szyprowski, PhD
>Samsung R&D Institute Poland
>
>
> return 0;
>
>
>Will submit the patch in a jiff. Thanks!
>
>
>
>>
>>Best regards
>>--
>>Marek Szyprowski, PhD
>>Samsung R&D Institute Poland
>>
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