Subject: Re: [PATCH net-next 0/9] mlx4: order-0 allocations and page recycling

From: Tariq Toukan <[email-masked]>
Date: Wed, 8 Feb 2017 11:02:01 +0200

On 07/02/2017 5:50 PM, Tariq Toukan wrote:
> Hi Eric,
>
> Thanks for your series.
>
> On 07/02/2017 5:02 AM, Eric Dumazet wrote:
>> As mentioned half a year ago, we better switch mlx4 driver to order-0
>> allocations and page recycling.
>>
>> This reduces vulnerability surface thanks to better skb->truesize 
>> tracking
>> and provides better performance in most cases.
> The series makes significant change in the RX data-path, that requires 
> deeper checks, in addition to code review.
> We applied your series and started running both our functional and 
> performance regression.
> We will have results by tomorrow morning, and will analyze them during 
> the day. I'll update about that.
We hit a kernel panic when running traffic after configuring a large MTU 
(9000).
I will take deeper look into this soon and will keep you updated.

[56136.982183] BUG: unable to handle kernel paging request at 
000000022f9e7020
[56136.990426] IP: mlx4_en_complete_rx_desc+0x130/0x2e0 [mlx4_en]
[56136.995303] PGD 220b7c067
[56136.995304] PUD 0
[56136.997941]
[56137.001807] Oops: 0000 [#1] SMP
[56137.004540] Modules linked in: netconsole mlx4_ib mlx4_en(E) 
mlx4_core(E) nfsv3 nfs fscache rpcrdma ib_isert iscsi_target_mod ib_iser 
libiscsi scsi_transport_iscsi ib_srpt target_core_mod ib_srp 
scsi_transport_srp ib_ipoib rdma_ucm ib_ucm ib_uverbs ib_umad rdma_cm 
dm_mirror dm_region_hash dm_log ib_cm dm_mod iw_cm ppdev parport_pc 
i2c_piix4 sg virtio_balloon parport pcspkr acpi_cpufreq nfsd auth_rpcgss 
nfs_acl lockd grace sunrpc ip_tables mlx5_ib sd_mod ata_generic 
pata_acpi ib_core mlx5_core cirrus drm_kms_helper syscopyarea 
sysfillrect sysimgblt fb_sys_fops ttm drm ata_piix floppy libata ptp 
e1000 crc32c_intel virtio_pci pps_core serio_raw virtio_ring i2c_core 
virtio [last unloaded: netconsole]
[56137.046028] CPU: 1 PID: 16 Comm: ksoftirqd/1 Tainted: G            
E   4.10.0-rc6+ #26
[56137.051501] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[56137.055817] task: ffff880236245200 task.stack: ffffc90000d04000
[56137.060154] RIP: 0010:mlx4_en_complete_rx_desc+0x130/0x2e0 [mlx4_en]
[56137.064712] RSP: 0018:ffffc90000d07c90 EFLAGS: 00010282
[56137.068646] RAX: 0000000000000003 RBX: 000000022f9e7000 RCX: 
ffff880234988880
[56137.073588] RDX: ffff8802349888e0 RSI: 0000000000000000 RDI: 
ffff880235dad0a0
[56137.078563] RBP: ffffc90000d07ce0 R08: 0000000000000000 R09: 
ffff8802225a08c0
[56137.083370] R10: ffff8802335c7800 R11: 0000000000000000 R12: 
ffffc90001da1048
[56137.088123] R13: 0000000000000b36 R14: ffff8802225af040 R15: 
0000000000000b36
[56137.092837] FS:  0000000000000000(0000) GS:ffff88023fc40000(0000) 
knlGS:0000000000000000
[56137.098495] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[56137.102626] CR2: 000000022f9e7020 CR3: 000000023441f000 CR4: 
00000000000006e0
[56137.107581] Call Trace:
[56137.109955]  mlx4_en_process_rx_cq+0x35c/0xda0 [mlx4_en]
[56137.113894]  ? mlx4_en_free_tx_desc+0x14e/0x350 [mlx4_en]
[56137.117992]  ? load_balance+0x1ac/0x900
[56137.121285]  mlx4_en_poll_rx_cq+0x30/0xa0 [mlx4_en]
[56137.125023]  net_rx_action+0x23d/0x3a0
[56137.128146]  __do_softirq+0xd1/0x2a2
[56137.131178]  run_ksoftirqd+0x29/0x50
[56137.134180]  smpboot_thread_fn+0x110/0x160
[56137.137530]  kthread+0x101/0x140
[56137.140330]  ? sort_range+0x30/0x30
[56137.143255]  ? kthread_park+0x90/0x90
[56137.146304]  ? __kthread_parkme+0x50/0x70
[56137.149466]  ret_from_fork+0x2c/0x40
[56137.152426] Code: c0 8b 45 cc 41 8b 8a cc 00 00 00 48 63 d0 49 03 8a 
d0 00 00 00 48 83 c2 03 48 c1 e2 04 48 01 ca 48 89 1a 44 89 5a 08 44 89 
7a 0c <48> 8b 53 20 f6 c2 01 0f 85 76 01 00 00 48 89 da 48 83 7a 10 ff
[56137.164855] RIP: mlx4_en_complete_rx_desc+0x130/0x2e0 [mlx4_en] RSP: 
ffffc90000d07c90
[56137.170211] CR2: 000000022f9e7020
[56137.175430] ---[ end trace 6a259f16967a0cff ]---

>>
>> Worth noting this patch series deletes more than 100 lines of code ;)
>>
>> Eric Dumazet (9):
>>    mlx4: use __skb_fill_page_desc()
>>    mlx4: dma_dir is a mlx4_en_priv attribute
>>    mlx4: remove order field from mlx4_en_frag_info
>>    mlx4: get rid of frag_prefix_size
>>    mlx4: rx_headroom is a per port attribute
>>    mlx4: reduce rx ring page_cache size
>>    mlx4: removal of frag_sizes[]
>>    mlx4: use order-0 pages for RX
>>    mlx4: add page recycling in receive path
>>
>>   drivers/net/ethernet/mellanox/mlx4/en_rx.c   | 350 
>> +++++++++------------------
>>   drivers/net/ethernet/mellanox/mlx4/en_tx.c   |   4 +-
>>   drivers/net/ethernet/mellanox/mlx4/mlx4_en.h |  28 +--
>>   3 files changed, 129 insertions(+), 253 deletions(-)
>>
> Thanks,
> Tariq