netdev - Re: 32 core net-next stack/netfilter "scaling"

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Date:	Tue, 27 Jan 2009 11:09:01 -0800
From:	Rick Jones <rick.jones2@...com>
To:	Rick Jones <rick.jones2@...com>
CC:	Patrick McHardy <kaber@...sh.net>,
	Eric Dumazet <dada1@...mosbay.com>,
	Linux Network Development list <netdev@...r.kernel.org>,
	Netfilter Developers <netfilter-devel@...r.kernel.org>,
	Stephen Hemminger <shemminger@...tta.com>
Subject: Re: 32 core net-next stack/netfilter "scaling"

Rick Jones wrote:
> Patrick McHardy wrote:
> 
>> Eric Dumazet wrote:
>>
>>> [PATCH] netfilter: Get rid of central rwlock in tcp conntracking
>>>
>>> TCP connection tracking suffers of huge contention on a global rwlock,
>>> used to protect tcp conntracking state.
>>>
>>> As each tcp conntrack state have no relations between each others, we
>>> can switch to fine grained lock. Using an array of spinlocks avoids
>>> enlarging size of connection tracking structures, yet giving reasonable
>>> fanout.
>>>
>>> tcp_print_conntrack() doesnt need to lock anything to read
>>> ct->proto.tcp.state, so speedup /proc/net/ip_conntrack as well.
>>>
>>> nf_conntrack_hash_rnd_initted & nf_conntrack_hash_rnd declared 
>>> read_mostly
>>>  
>>
>>
>>
>> This looks good to me. Rick, would you like to give it a try?
>>
>> I'll convert the remaining conntrack protocols when applying it.
> 
> 
> I will give it a try and let folks know the results - unless told 
> otherwise, I will ass-u-me I only need rerun the "full_iptables" test case.

The runemomniagg2.sh script is still running, but the initial cycles profile 
suggests that the main change is converting the write_lock time into spinlock 
contention time with 78.39% of the cycles spent in ia64_spinlock_contention. 
When the script completes I'll upload the profiles and the netperf results to the 
same base URL as in the basenote under "contrack01/"

rick jones
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