Date:   Mon, 22 Jan 2018 10:44:33 -0800
From:   Ben Greear <greearb@...delatech.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: TCP many-connection regression between 4.7 and 4.13 kernels.

On 01/22/2018 10:30 AM, Ben Greear wrote:
> On 01/22/2018 10:16 AM, Eric Dumazet wrote:
>> On Mon, 2018-01-22 at 09:28 -0800, Ben Greear wrote:
>>> My test case is to have 6 processes each create 5000 TCP IPv4 connections to each other
>>> on a system with 16GB RAM and send slow-speed data.  This works fine on a 4.7 kernel, but
>>> will not work at all on a 4.13.  The 4.13 first complains about running out of tcp memory,
>>> but even after forcing those values higher, the max connections we can get is around 15k.
>>>
>>> Both kernels have my out-of-tree patches applied, so it is possible it is my fault
>>> at this point.
>>>
>>> Any suggestions as to what this might be caused by, or if it is fixed in more recent kernels?
>>>
>>> I will start bisecting in the meantime...
>>>
>>
>> Hi Ben
>>
>> Unfortunately I have no idea.
>>
>> Are you using loopback flows, or have I misunderstood you ?
>>
>> How loopback connections can be slow-speed ?
>>
>
> I am sending to self, but over external network interfaces, by using
> routing tables and rules and such.
>
> On 4.13.16+, I see the Intel driver bouncing when I try to start 20k
> connections.  In this case, I have a pair of 10G ports doing 15k, and then
> I try to start 5k on two of the 1G ports....
>
> Jan 22 10:15:41 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Down
> Jan 22 10:15:41 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: Rx/Tx
> Jan 22 10:15:41 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Down
> Jan 22 10:15:41 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: Rx/Tx
> Jan 22 10:15:41 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Down
> Jan 22 10:15:41 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: Rx/Tx
> Jan 22 10:15:43 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Down
> Jan 22 10:15:45 lf1003-e3v2-13100124-f20x64 kernel: e1000e: eth3 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: Rx/Tx
> Jan 22 10:15:51 lf1003-e3v2-13100124-f20x64 kernel: NETDEV WATCHDOG: eth3 (e1000e): transmit queue 0 timed out, trans_s...es: 1
> Jan 22 10:15:51 lf1003-e3v2-13100124-f20x64 kernel: e1000e 0000:07:00.0 eth3: Reset adapter unexpectedly
>
>
> System reports 10+GB RAM free in this case, btw.
>
> Actually, maybe the good kernel was even older than 4.7...I see same resets and inability to do a full 20k
> connections on 4.7 too.   I double-checked with system-test and it seems 4.4 was a good kernel.  I'll test
> that next.  Here is splat from 4.7:
>
> [  238.921679] ------------[ cut here ]------------
> [  238.921689] WARNING: CPU: 0 PID: 3 at /home/greearb/git/linux-bisect/net/sched/sch_generic.c:272 dev_watchdog+0xd4/0x12f
> [  238.921690] NETDEV WATCHDOG: eth3 (e1000e): transmit queue 0 timed out
> [  238.921691] Modules linked in: nf_conntrack_netlink nf_conntrack nfnetlink nf_defrag_ipv4 cfg80211 macvlan pktgen bnep bluetooth fuse coretemp intel_rapl
> ftdi_sio x86_pkg_temp_thermal intel_powerclamp kvm_intel kvm iTCO_wdt iTCO_vendor_support joydev ie31200_edac ipmi_devintf irqbypass serio_raw ipmi_si edac_core
> shpchp fjes video i2c_i801 tpm_tis lpc_ich ipmi_msghandler tpm nfsd auth_rpcgss nfs_acl lockd grace sunrpc mgag200 i2c_algo_bit drm_kms_helper ttm drm i2c_core
> e1000e ixgbe mdio hwmon dca ptp pps_core ipv6 [last unloaded: nf_conntrack]
> [  238.921720] CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.7.0 #62
> [  238.921721] Hardware name: Supermicro X9SCI/X9SCA/X9SCI/X9SCA, BIOS 2.0b 09/17/2012
> [  238.921723]  0000000000000000 ffff88041cdd7cd8 ffffffff81352a23 ffff88041cdd7d28
> [  238.921725]  0000000000000000 ffff88041cdd7d18 ffffffff810ea5dd 000001101cdd7d90
> [  238.921727]  ffff880417a84000 0000000000000100 ffffffff8163ecff ffff880417a84440
> [  238.921728] Call Trace:
> [  238.921733]  [<ffffffff81352a23>] dump_stack+0x61/0x7d
> [  238.921736]  [<ffffffff810ea5dd>] __warn+0xbd/0xd8
> [  238.921738]  [<ffffffff8163ecff>] ? netif_tx_lock+0x81/0x81
> [  238.921740]  [<ffffffff810ea63e>] warn_slowpath_fmt+0x46/0x4e
> [  238.921741]  [<ffffffff8163ecf2>] ? netif_tx_lock+0x74/0x81
> [  238.921743]  [<ffffffff8163edd3>] dev_watchdog+0xd4/0x12f
> [  238.921746]  [<ffffffff8113cfbb>] call_timer_fn+0x65/0x11b
> [  238.921748]  [<ffffffff8163ecff>] ? netif_tx_lock+0x81/0x81
> [  238.921749]  [<ffffffff8113d73e>] run_timer_softirq+0x1ad/0x1d7
> [  238.921751]  [<ffffffff810ee701>] __do_softirq+0xfb/0x25c
> [  238.921752]  [<ffffffff810ee87b>] run_ksoftirqd+0x19/0x35
> [  238.921755]  [<ffffffff81105ae8>] smpboot_thread_fn+0x169/0x1a9
> [  238.921756]  [<ffffffff8110597f>] ? sort_range+0x1d/0x1d
> [  238.921759]  [<ffffffff811031a1>] kthread+0xa0/0xa8
> [  238.921763]  [<ffffffff816ce19f>] ret_from_fork+0x1f/0x40
> [  238.921764]  [<ffffffff81103101>] ? init_completion+0x24/0x24
> [  238.921765] ---[ end trace 933912956c6ee5ff ]---
> [  238.961672] e1000e 0000:07:00.0 eth3: Reset adapter unexpectedly

So, on 4.4.8+, I see this and other splats related to e1000e.  I guess that is a separate
issue.  I can easily start 40k connections however, 30k across the two 10G ports,
and 10k more across a pair of mac-vlans on the 10G ports (since I was out of
address space to add a full 40k on the two physical ports).


Looks like the e1000e problem is a separate issue, so I'll just focus on the 10G NIC for now.

Thanks,
Ben


-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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