netdev - Re: ping6 packets high probability loss occurs by the default firewalld rule(rpfilter invert) with low traffic generated by iperf

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Date:   Mon, 11 Nov 2019 18:35:31 -0700
From:   David Ahern <dsahern@...il.com>
To:     hujunwei <hujunwei4@...wei.com>,
        Eric Dumazet <eric.dumazet@...il.com>, davem@...emloft.net,
        kafai@...com, weiwan@...gle.com
Cc:     netdev@...r.kernel.org, wangxiaogang3@...wei.com,
        xuhanbing@...wei.com, Wei Wang <weiwan@...gle.com>,
        Martin KaFai Lau <kafai@...com>
Subject: Re: ping6 packets high probability loss occurs by the default
 firewalld rule(rpfilter invert) with low traffic generated by iperf

On 11/11/19 6:26 PM, hujunwei wrote:
> 
> On 2019/11/4 10:29, hujunwei wrote:
>>
>>
>> On 2019/11/4 2:53, Eric Dumazet wrote:
>>>
>>> By how much have you increased gc_thresh ?
>>>
>>> I wonder if you are not hit by RCU being unable to drain its queue fast enough.
>>>
>>> Could you try backporting :
>>>
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cfcdef5e30469f3f2d6786ad35fc3fdef2a3833f
>>>
>>> But the default gc_thresh of 1024 might be too small for this patch
>>> to make any difference, since (1024 >> 7) is 8 
>>>
>>>
>>
>> Hi Eric,
>> Thanks for your reply, I set gc_thresh to 10240 last time. I will backport and test the patch later.
>>
>> Regards Junwei
>>
> 
> Hi Eric,
> I applied the patch and find packetes still drop with default value of gc_thresh.
> I will submit a patch later.
> 
> Regards Junwei
> 

perhaps it is time to update IPv6's gc_thresh to match IPv4's - meaning
it stays but gets set to -1 and is not used. Is there a reason to keep a
limit these days?