Re: Linux 5.0 regression: rtl8169 / kernel BUG at lib/dynamic_queue_limits.c:27!

From: Sander Eikelenboom
Date: Sun Feb 10 2019 - 08:04:12 EST

On 10/02/2019 12:44, Heiner Kallweit wrote:
> On 10.02.2019 10:16, Sander Eikelenboom wrote:
>> On 09/02/2019 12:50, Heiner Kallweit wrote:
>>> On 09.02.2019 11:07, Sander Eikelenboom wrote:
>>>> On 09/02/2019 10:59, Heiner Kallweit wrote:
>>>>> On 09.02.2019 10:34, Sander Eikelenboom wrote:
>>>>>> On 09/02/2019 10:02, Heiner Kallweit wrote:
>>>>>>> On 09.02.2019 00:09, Eric Dumazet wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> On 02/08/2019 01:50 PM, Heiner Kallweit wrote:
>>>>>>>>> On 08.02.2019 22:45, Sander Eikelenboom wrote:
>>>>>>>>>> On 08/02/2019 22:22, Heiner Kallweit wrote:
>>>>>>>>>>> On 08.02.2019 21:55, Sander Eikelenboom wrote:
>>>>>>>>>>>> On 08/02/2019 19:52, Heiner Kallweit wrote:
>>>>>>>>>>>>> On 08.02.2019 19:29, Sander Eikelenboom wrote:
>>>>>>>>>>>>>> L.S.,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> While testing a linux 5.0-rc5 kernel (with some patches on top but they don't seem related) under Xen i the nasty splat below,
>>>>>>>>>>>>>> that I haven encountered with Linux 4.20.x.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Unfortunately I haven't got a clear reproducer for this and bisecting could be nasty due to another (networking related) kernel bug.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> If you need more info, want me to run a debug patch etc., please feel free to ask.
>>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks for the report. However I see no change in the r8169 driver between
>>>>>>>>>>>>> 4.20 and 5.0 with regard to BQL code. Having said that the root cause could
>>>>>>>>>>>>> be somewhere else. Therefore I'm afraid a bisect will be needed.
>>>>>>>>>>>>
>>>>>>>>>>>> Hmm i did some diging and i think:
>>>>>>>>>>>> bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 r8169: remove unneeded mmiowb barriers
>>>>>>>>>>>> 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 r8169: make use of xmit_more and __netdev_sent_queue
>>>>>>>>>>>> 620344c43edfa020bbadfd81a144ebe5181fc94f net: core: add __netdev_sent_queue as variant of __netdev_tx_sent_queue
>>>>>>>>>>>>
>>>>>>>>>>> You're right. Thought this was added in 4.20 already.
>>>>>>>>>>> The BQL code pattern I copied from the mlx4 driver and so far I haven't heard about
>>>>>>>>>>> this issue from any user of physical hw. And due to the fact that a lot of mainboards
>>>>>>>>>>> have onboard Realtek network I have quite a few testers out there.
>>>>>>>>>>> Does the issue occur under specific circumstances like very high load?
>>>>>>>>>>
>>>>>>>>>> Yep, the box is already quite contented with the Xen VM's and if I remember correctly it occurred while kernel compiling
>>>>>>>>>> on the host.
>>>>>>>>>>
>>>>>>>>>>> If indeed the xmit_more patch causes the issue, I think we have to involve Eric Dumazet
>>>>>>>>>>> as author of the underlying changes.
>>>>>>>>>>
>>>>>>>>>> It could also be the barriers weren't that unneeded as assumed.
>>>>>>>>>
>>>>>>>>> The barriers were removed after adding xmit_more handling. Therefore it would be good to
>>>>>>>>> test also with only
>>>>>>>>> bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 r8169: remove unneeded mmiowb barriers
>>>>>>>>> removed.
>>>>>>>>>
>>>>>>>>>> Since we are almost at RC6 i took the liberty to CC Eric now.
>>>>>>>>>>
>>>>>>>>> Sure, thanks.
>>>>>>>>>
>>>>>>>>>> BTW am i correct these patches are merely optimizations ?
>>>>>>>>>
>>>>>>>>> Yes
>>>>>>>>>
>>>>>>>>>> If so and concluding they revert cleanly, perhaps it should be considered at this point in the RC's
>>>>>>>>>> to revert them for 5.0 and try again for 5.1 ?
>>>>>>>>>>
>>>>>>>>> Before removing both it would be good to test with only the barrier-removal removed.
>>>>>>>>>
>>>>>>>>
>>>>>>>> Commit 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 r8169: make use of xmit_more and __netdev_sent_queue
>>>>>>>> looks buggy to me, since the skb might have been freed already on another cpu when you call
>>>>>>>>
>>>>>>>> You could try :
>>>>>>>>
>>>>>>>> diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
>>>>>>>> index 3624e67aef72c92ed6e908e2c99ac2d381210126..f907d484165d9fd775e81bf2bfb9aa4ddedb1c93 100644
>>>>>>>> --- a/drivers/net/ethernet/realtek/r8169.c
>>>>>>>> +++ b/drivers/net/ethernet/realtek/r8169.c
>>>>>>>> @@ -6070,6 +6070,7 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>>>>> dma_addr_t mapping;
>>>>>>>> u32 opts[2], len;
>>>>>>>> bool stop_queue;
>>>>>>>> + bool door_bell;
>>>>>>>> int frags;
>>>>>>>>
>>>>>>>> if (unlikely(!rtl_tx_slots_avail(tp, skb_shinfo(skb)->nr_frags))) {
>>>>>>>> @@ -6116,6 +6117,8 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>>>>> /* Force memory writes to complete before releasing descriptor */
>>>>>>>> dma_wmb();
>>>>>>>>
>>>>>>>> + door_bell = __netdev_sent_queue(dev, skb->len, skb->xmit_more);
>>>>>>>> +
>>>>>>>> txd->opts1 = rtl8169_get_txd_opts1(opts[0], len, entry);
>>>>>>>>
>>>>>>>> /* Force all memory writes to complete before notifying device */
>>>>>>>> @@ -6127,7 +6130,7 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>>>>> if (unlikely(stop_queue))
>>>>>>>> netif_stop_queue(dev);
>>>>>>>>
>>>>>>>> - if (__netdev_sent_queue(dev, skb->len, skb->xmit_more)) {
>>>>>>>> + if (door_bell) {
>>>>>>>> RTL_W8(tp, TxPoll, NPQ);
>>>>>>>> mmiowb();
>>>>>>>> }
>>>>>>>>
>>>>>>> Thanks a lot for checking and for the proposed fix.
>>>>>>> Sander, can you try with this patch on top of 5.0-rc5 w/o removing two two commits?
>>>>>>
>>>>>> I have done that already during the night .. the results:
>>>>>> - I can confirm 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 is the first commit which causes hitting the BUG_ON in lib/dynamic_queue_limits.c.
>>>>>> (in other word, with only reverting bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 it still blows up).
>>>>>>
>>>>>> - The Eric's patch only applies cleanly with bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 reverted, so that's what I tested.
>>>>>> The patch seems to prevent hitting the BUG_ON in lib/dynamic_queue_limits.c, it has run this night and I gave done a few kernel compiles
>>>>>> this morning. How ever during these kernel compiles i'm getting a transmit queue timeout which i haven't seen with 4.20.x, although i regularly
>>>>>> compile kernels in the same way as I do now. The only thing I can't say if that is due to this change, or if it's again something else.
>>>>>> Which makes me somewhat inclined to go testing the complete revert some more and see if I can trigger the queue timeout on that or not.
>>>>>>
>>>>>> If I can, it is a separate issue.
>>>>>> If I can't it seems even with a patch it still seems as a regression in comparison with 4.20.x, for which
>>>>>> a revert would be the right thing to do (since as you indicated these are merely optimizations),
>>>>>> which would give us more time for 5.1 to try to solve things on top of the 5.0-release-to-be.
>>>>>> (especially since I seem to still have other issues which need to be sorted out and time is limited)
>>>>>>
>>>>>> The timeout in question:
>>>>>> [28336.869479] NETDEV WATCHDOG: eth1 (r8169): transmit queue 0 timed out
>>>>>> [28336.881498] WARNING: CPU: 0 PID: 6925 at net/sched/sch_generic.c:461 dev_watchdog+0x20b/0x210
>>>>>> [28336.893358] Modules linked in:
>>>>>> [28336.904106] CPU: 0 PID: 6925 Comm: cc1 Tainted: G D 5.0.0-rc5-20190208-thp-net-florian-rtl8169-eric-doflr+ #1
>>>>>> [28336.917385] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640) , BIOS V1.8B1 09/13/2010
>>>>>> [28336.928988] RIP: e030:dev_watchdog+0x20b/0x210
>>>>>> [28336.940623] Code: 00 49 63 4e e0 eb 90 4c 89 e7 c6 05 ad d8 f1 00 01 e8 a9 32 fd ff 89 d9 48 89 c2 4c 89 e6 48 c7 c7 50 59 89 82 e8 e5 92 4d ff <0f> 0b eb c0 90 48 c7 47 08 00 00 00 00 48 c7 07 00 00 00 00 0f b7
>>>>>> [28336.965265] RSP: e02b:ffff88807d403ea0 EFLAGS: 00010286
>>>>>> [28336.977465] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff82a69db8
>>>>>> [28336.991265] RDX: 0000000000000001 RSI: 0000000000000001 RDI: 0000000000000200
>>>>>> [28337.008865] RBP: ffff88807936e41c R08: 0000000000000000 R09: 0000000000000819
>>>>>> [28337.022250] R10: 0000000000000202 R11: ffffffff8247ca80 R12: ffff88807936e000
>>>>>> [28337.035204] R13: 0000000000000000 R14: ffff88807936e440 R15: 0000000000000001
>>>>>> [28337.049832] FS: 00007f53e9bf3840(0000) GS:ffff88807d400000(0000) knlGS:0000000000000000
>>>>>> [28337.062524] CS: e030 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>> [28337.075086] CR2: 00007f53e60c4000 CR3: 000000001a0be000 CR4: 0000000000000660
>>>>>> [28337.090052] Call Trace:
>>>>>> [28337.103615] <IRQ>
>>>>>> [28337.116587] ? qdisc_destroy+0x120/0x120
>>>>>> [28337.128905] call_timer_fn+0x19/0x90
>>>>>> [28337.141892] expire_timers+0x8b/0xa0
>>>>>> [28337.153354] run_timer_softirq+0x7e/0x160
>>>>>> [28337.165931] ? handle_irq_event_percpu+0x4c/0x70
>>>>>> [28337.176548] ? handle_percpu_irq+0x32/0x50
>>>>>> [28337.186734] __do_softirq+0xed/0x229
>>>>>> [28337.196404] ? hypervisor_callback+0xa/0x20
>>>>>> [28337.207822] irq_exit+0xb7/0xc0
>>>>>> [28337.218978] xen_evtchn_do_upcall+0x27/0x40
>>>>>> [28337.230763] xen_do_hypervisor_callback+0x29/0x40
>>>>>> [28337.241261] </IRQ>
>>>>>> [28337.253283] RIP: e033:0xff7e62
>>>>>> [28337.264899] Code: 35 43 0f c7 00 4c 89 ef e8 8b 6d 67 ff 0f 1f 00 44 89 e0 44 89 e2 c1 e8 06 83 e2 3f 48 8b 0c c5 40 8d c6 01 48 0f a3 d1 72 0e <48> 8b 04 c5 50 8d c6 01 48 0f a3 d0 73 0b 44 89 e6 4c 89 ef e8 b5
>>>>>> [28337.288677] RSP: e02b:00007fff0fc6a340 EFLAGS: 00000202
>>>>>> [28337.299234] RAX: 0000000000000000 RBX: 00007f53e60c3580 RCX: 0000000000000000
>>>>>> [28337.309577] RDX: 0000000000000034 RSI: 0000000001e71a98 RDI: 00007fff0fc6a538
>>>>>> [28337.320724] RBP: 00007fff0fc6a4b0 R08: 0000000000000000 R09: 0000000000000000
>>>>>> [28337.331829] R10: 0000000000000001 R11: 00000000020cb3d0 R12: 0000000000000034
>>>>>> [28337.343900] R13: 00007fff0fc6a538 R14: 0000000000000000 R15: 0000000000000001
>>>>>> [28337.353977] ---[ end trace 6ff49f09286816b7 ]---
>>>>>>
>>>>> Thanks for your efforts. As usual this tx timeout trace says basically nothing except
>>>>> "timeout" and root cause could be anything. Earlier you reported a memory allocation error,
>>>>> did that occur again?
>>>>> If we decide to revert, I'd leave removal of the memory barriers in (as it doesn't seem to
>>>>> contribute to the issue) and just submit a patch to effectively revert
>>>>> 2e6eedb4813e34d8d84ac0eb3afb668966f3f356.
>>>>
>>>> I can't say if that is correct, because i haven't tested that.
>>>>
>>>> Another thing I could test is:
>>>> - putting all the r8169 patches (and prerequisites) that went into 5.0
>>>> up to bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3, onto 4.20.7 and see what that does.
>>>> If that would be feasible (not too many needed prerequisites out of r8169) and if
>>>> you could spare me some time and prep such a branch somewhere so i can pull and compile that,
>>>> that would be great.
>>>>
>>>
>>> Unfortunately there's quite a number of changes. Regarding __netdev_tx_sent_queue()
>>> and watchdog timeout I found the following comment in drivers/net/ethernet/sfc/tx.c,
>>> efx_enqueue_skb():
>>>
>>> if (__netdev_tx_sent_queue(tx_queue->core_txq, skb_len, xmit_more)) {
>>> struct efx_tx_queue *txq2 = efx_tx_queue_partner(tx_queue);
>>>
>>> /* There could be packets left on the partner queue if those
>>> * SKBs had skb->xmit_more set. If we do not push those they
>>> * could be left for a long time and cause a netdev watchdog.
>>> */
>>> if (txq2->xmit_more_available)
>>> efx_nic_push_buffers(txq2);
>>>
>>> But I'm not sure whether the situation in r8169 is comparable. The following patch
>>> implements what I mentioned earlier: It leaves all other 5.0 changes in place and
>>> effectively reverts 2e6eedb4813e34d8d84ac0eb3afb668966f3f356. Would be great if
>>> you could give it a try.
>>
>> Hi Heiner,
>>
>> It took some time to respond, because I had another issue with 5.0 which intervened with proper testing,
>> but fortunately I could pinpoint without doing a full bisect and revert that commit for further testing.
>>
>> So there is still time left and I could do a more proper run with your patch below.
>> Unfortunately i still get a splat (see below) with this, although i'm not sure it is related,
>> just that I can't tell.
>>
> I checked further and there's a handful of network drivers using __napi_alloc_skb() with __GFP_NOWARN,
> maybe to avoid such splats. Did the splat impact functionality? When checking the code in r8169 the
> affected packet would just be dropped.

It doesn't permanently or noticeably impact functionality, and indeed seems to drop packets:

eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.16.1.1 netmask 255.255.0.0 broadcast 172.16.255.255
ether 40:61:86:f4:67:d8 txqueuelen 1000 (Ethernet)
RX packets 11563913 bytes 16724445852 (15.5 GiB)
RX errors 0 dropped 6 overruns 0 frame 0
TX packets 4301515 bytes 1210966808 (1.1 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Reverting 5317d5c6d47e ("r8169: use napi_consume_skb where possible") doesn't suffice still gives the page allocation failure.

I think at this point in time we should at least get the
reverts into 5.0 (probably to late for rc-6 since DaveM's pull request is already in) for:
bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 r8169: remove unneeded mmiowb barriers
2e6eedb4813e34d8d84ac0eb3afb668966f3f356 r8169: make use of xmit_more and __netdev_sent_queue

Commit 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 is the one which caused the BUG_ON() to be hit.

While we could use your patch to revert only 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 and leave
bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 in:
- I haven't been able to test it properly.
- It's dealing with barriers, which can be tedious and give subtle breakage.
- I don't see any compelling argument to keep it in (it's no fix).
- It's RC-6 time ...

So we then we can focus on the page allocation issue and hopefully find some stable
baseline before 5.0-final is cut. While I appreciate having a forward looking approach,
I think we are at the point in time, were we should revert when in doubt
(and it doesn't clearly fix an other issue).

After establishing a stable baseline again, we can start incrementally re-applying and test stuff.

--
Sander



>> Perhaps Linus as Oops-decoding-guru has an idea ?
>>
>> --
>> Sander
>>
>> [39041.689007] dpkg-deb: page allocation failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null),cpuset=/,mems_allowed=0
>> [39041.689016] CPU: 4 PID: 14078 Comm: dpkg-deb Not tainted 5.0.0-rc5-20190209-kallweit+ #1
>> [39041.689017] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640) , BIOS V1.8B1 09/13/2010
>> [39041.689018] Call Trace:
>> [39041.689022] <IRQ>
>> [39041.689030] dump_stack+0x5c/0x7b
>> [39041.689033] warn_alloc+0x103/0x190
>> [39041.689036] __alloc_pages_nodemask+0xe3d/0xe80
>> [39041.689039] ? ip_rcv+0x48/0xc0
>> [39041.689040] ? ip_rcv_finish_core.isra.0+0x360/0x360
>> [39041.689042] page_frag_alloc+0x117/0x150
>> [39041.689044] __napi_alloc_skb+0x83/0xd0
>> [39041.689048] rtl8169_poll+0x210/0x640
>> [39041.689051] net_rx_action+0x23d/0x370
>> [39041.689054] __do_softirq+0xed/0x229
>> [39041.689058] irq_exit+0xb7/0xc0
>> [39041.689061] xen_evtchn_do_upcall+0x27/0x40
>> [39041.689063] xen_do_hypervisor_callback+0x29/0x40
>> [39041.689064] </IRQ>
>> [39041.689066] RIP: e030:_atomic_dec_and_lock+0x2/0x40
>> [39041.689068] Code: ff 39 05 c5 c1 c9 00 89 c7 89 c6 76 0f 83 eb 01 83 fb ff 75 d9 5b 89 f8 5d 41 5c c3 0f 0b 90 90 90 90 90 90 90 90 90 90 8b 07 <83> f8 01 74 0c 8d 50 ff f0 0f b1 17 75 f2 31 c0 c3 55 53 48 89 fb
>> [39041.689069] RSP: e02b:ffffc9000705b990 EFLAGS: 00000246
>> [39041.689071] RAX: 0000000000000001 RBX: ffff888017082640 RCX: 0000000000000000
>> [39041.689071] RDX: 0000000000000000 RSI: ffff8880170826c0 RDI: ffff888017082788
>> [39041.689072] RBP: ffff8880170826c0 R08: ffffc9000705bb00 R09: ffffc9000705bb00
>> [39041.689073] R10: ffffc9000705bb58 R11: ffff88807fc17000 R12: ffff888017082788
>> [39041.689073] R13: ffff88806cc8cf58 R14: ffff888017082640 R15: ffff888009990240
>> [39041.689077] iput+0x63/0x1a0
>> [39041.689079] __dentry_kill+0xc5/0x170
>> [39041.689080] shrink_dentry_list+0x93/0x1c0
>> [39041.689082] prune_dcache_sb+0x4d/0x70
>> [39041.689084] super_cache_scan+0x104/0x190
>> [39041.689087] do_shrink_slab+0x12c/0x1e0
>> [39041.689089] shrink_slab+0xdf/0x2b0
>> [39041.689091] shrink_node+0x158/0x470
>> [39041.689093] do_try_to_free_pages+0xd1/0x380
>> [39041.689095] try_to_free_pages+0xb2/0xe0
>> [39041.689097] __alloc_pages_nodemask+0x603/0xe80
>> [39041.689099] ? __pagevec_lru_add_fn+0x1b1/0x290
>> [39041.689102] alloc_pages_vma+0x7b/0x1c0
>> [39041.689106] __handle_mm_fault+0xdb3/0x1060
>> [39041.689109] ? xen_mc_flush+0xc0/0x190
>> [39041.689110] handle_mm_fault+0xf8/0x200
>> [39041.689113] __do_page_fault+0x231/0x4a0
>> [39041.689115] ? page_fault+0x8/0x30
>> [39041.689116] page_fault+0x1e/0x30
>> [39041.689118] RIP: e033:0x7fb9851d012e
>> [39041.689119] Code: 29 c2 48 3b 15 7b a3 31 00 0f 87 af 00 00 00 0f 10 01 0f 10 49 f0 0f 10 51 e0 0f 10 59 d0 48 83 e9 40 48 83 ea 40 41 0f 29 01 <41> 0f 29 49 f0 41 0f 29 51 e0 41 0f 29 59 d0 49 83 e9 40 48 83 fa
>> [39041.689119] RSP: e02b:00007fb958b36d38 EFLAGS: 00010202
>> [39041.689120] RAX: 00007fb97a617f0e RBX: 000000000000f004 RCX: 00007fb948008be3
>> [39041.689121] RDX: 00000000000080c2 RSI: 00007fb948000b31 RDI: 00007fb97a617f0e
>> [39041.689122] RBP: 00000000000ff062 R08: 0000000000000002 R09: 00007fb97a620000
>> [39041.689123] R10: 0000000000000004 R11: 00007fb97a626f02 R12: 000000000000f005
>> [39041.689123] R13: 00007fb948000b28 R14: 0000562d76b63710 R15: 0000000000000003
>> [39041.689125] Mem-Info:
>> [39041.689130] active_anon:78775 inactive_anon:49211 isolated_anon:0
>> active_file:106409 inactive_file:107531 isolated_file:0
>> unevictable:552 dirty:175 writeback:0 unstable:0
>> slab_reclaimable:13739 slab_unreclaimable:16454
>> mapped:1605 shmem:23 pagetables:2900 bounce:0
>> free:3681 free_pcp:935 free_cma:0
>> [39041.689132] Node 0 active_anon:315100kB inactive_anon:196844kB active_file:425636kB inactive_file:430124kB unevictable:2208kB isolated(anon):0kB isolated(file):0kB mapped:6420kB dirty:700kB writeback:0kB shmem:92kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
>> [39041.689133] Node 0 DMA free:7480kB min:44kB low:56kB high:68kB active_anon:0kB inactive_anon:7832kB active_file:472kB inactive_file:4kB unevictable:0kB writepending:0kB present:15956kB managed:15872kB mlocked:0kB kernel_stack:0kB pagetables:12kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
>> [39041.689136] lowmem_reserve[]: 0 1865 1865 1865
>> [39041.689138] Node 0 DMA32 free:7244kB min:19472kB low:21380kB high:23288kB active_anon:315360kB inactive_anon:188144kB active_file:425164kB inactive_file:430120kB unevictable:2208kB writepending:700kB present:2080768kB managed:1674968kB mlocked:2208kB kernel_stack:9632kB pagetables:11588kB bounce:0kB free_pcp:3740kB local_pcp:528kB free_cma:0kB
>> [39041.689140] lowmem_reserve[]: 0 0 0 0
>> [39041.689142] Node 0 DMA: 6*4kB (UME) 6*8kB (UE) 7*16kB (UME) 6*32kB (ME) 5*64kB (UME) 3*128kB (UE) 5*256kB (UME) 2*512kB (ME) 2*1024kB (UE) 1*2048kB (M) 0*4096kB = 7480kB
>> [39041.689148] Node 0 DMA32: 69*4kB (U) 315*8kB (UE) 138*16kB (UE) 70*32kB (UE) 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 7244kB
>> [39041.689153] 214701 total pagecache pages
>> [39041.689155] 273 pages in swap cache
>> [39041.689156] Swap cache stats: add 100978, delete 100706, find 1158/1257
>> [39041.689156] Free swap = 3790588kB
>> [39041.689157] Total swap = 4194300kB
>> [39041.689157] 524181 pages RAM
>> [39041.689158] 0 pages HighMem/MovableOnly
>> [39041.689158] 101471 pages reserved
>> [39041.689159] 0 pages cma reserved
>>
>>
>>
>>
>>
>>> diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
>>> index e8a112149..3cca2ffb2 100644
>>> --- a/drivers/net/ethernet/realtek/r8169.c
>>> +++ b/drivers/net/ethernet/realtek/r8169.c
>>> @@ -6192,7 +6192,6 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>> struct device *d = tp_to_dev(tp);
>>> dma_addr_t mapping;
>>> u32 opts[2], len;
>>> - bool stop_queue;
>>> int frags;
>>>
>>> if (unlikely(!rtl_tx_slots_avail(tp, skb_shinfo(skb)->nr_frags))) {
>>> @@ -6234,6 +6233,8 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>
>>> txd->opts2 = cpu_to_le32(opts[1]);
>>>
>>> + netdev_sent_queue(dev, skb->len);
>>> +
>>> skb_tx_timestamp(skb);
>>>
>>> /* Force memory writes to complete before releasing descriptor */
>>> @@ -6246,14 +6247,14 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>
>>> tp->cur_tx += frags + 1;
>>>
>>> - stop_queue = !rtl_tx_slots_avail(tp, MAX_SKB_FRAGS);
>>> - if (unlikely(stop_queue))
>>> - netif_stop_queue(dev);
>>> -
>>> - if (__netdev_sent_queue(dev, skb->len, skb->xmit_more))
>>> - RTL_W8(tp, TxPoll, NPQ);
>>> + RTL_W8(tp, TxPoll, NPQ);
>>>
>>> - if (unlikely(stop_queue)) {
>>> + if (!rtl_tx_slots_avail(tp, MAX_SKB_FRAGS)) {
>>> + /* Avoid wrongly optimistic queue wake-up: rtl_tx thread must
>>> + * not miss a ring update when it notices a stopped queue.
>>> + */
>>> + smp_wmb();
>>> + netif_stop_queue(dev);
>>> /* Sync with rtl_tx:
>>> * - publish queue status and cur_tx ring index (write barrier)
>>> * - refresh dirty_tx ring index (read barrier).
>>>
>>
>>
>