netdev - Re: High Cpu load when run smartdns : __ipv6_dev_get

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Message-Id: <4898B1F7-2EB5-4182-9D8D-FC8FC780E9B7@gmail.com>
Date: Sun, 27 Aug 2023 23:17:42 +0300
From: Martin Zaharinov <micron10@...il.com>
To: David Ahern <dsahern@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
 Eric Dumazet <edumazet@...gle.com>,
 pymumu@...il.com
Subject: Re: High Cpu load when run smartdns : __ipv6_dev_get_saddr

Hi David,



> On 27 Aug 2023, at 19:51, David Ahern <dsahern@...nel.org> wrote:
> 
> On 8/27/23 7:20 AM, Martin Zaharinov wrote:
>> Hi Eric 
>> 
>> 
>> i need you help to find is this bug or no.
>> 
>> I talk with smartdns team and try to research in his code but for the moment not found ..
>> 
>> test system have 5k ppp users on pppoe device
>> 
>> after run smartdns  
>> 
>> service got to 100% load 
>> 
>> in normal case when run other 2 type of dns server (isc bind or knot ) all is fine .
>> 
>> but when run smartdns  see perf : 
>> 
>> 
>> PerfTop:    4223 irqs/sec  kernel:96.9%  exact: 100.0% lost: 0/0 drop: 0/0 [4000Hz cycles],  (target_pid: 1208268)
>> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>> 
>>    28.48%  [kernel]        [k] __ipv6_dev_get_saddr
>>    12.31%  [kernel]        [k] l3mdev_master_ifindex_rcu
>>     6.63%  [pppoe]         [k] pppoe_rcv
>>     3.82%  [kernel]        [k] ipv6_dev_get_saddr
>>     2.07%  [kernel]        [k] __dev_queue_xmit
> 
> Can you post stack traces for the top 5 symbols?

If write how i will get.

> 
> What is the packet rate when the above is taken?

its normal rate of dns query… with both other dns server all is fine 

> 
> 4,223 irqs/sec is not much of a load; can you add some details on the
> hardware and networking setup (e.g., l3mdev reference suggests you are
> using VRF)?
No system is very simple:

eth0 (Internet) Router (smartDNS + pppoe server ) - eth1 ( User side with pppoe server ) here have 5000 ppp interface .

with both other service i dont see all work fine.


Here i will add in CC and Nick Peng he is developer of SmartDNS i he have idea ….


m.