netdev - Re: [PATCH 1/2] rhashtable: Introduce rhashtable_walk

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Message-Id: <20150127.141018.1208673547021029175.davem@davemloft.net>
Date:	Tue, 27 Jan 2015 14:10:18 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	tgraf@...g.ch, David.Laight@...LAB.COM, ying.xue@...driver.com,
	kaber@...sh.net, paulmck@...ux.vnet.ibm.com,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 1/2] rhashtable: Introduce rhashtable_walk_*

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Wed, 28 Jan 2015 07:39:24 +1100

> On Tue, Jan 27, 2015 at 11:40:28AM +0000, Thomas Graf wrote:
>> 
>> This is unrelated to resize run control though, the reason is that
>> I'm converting tcp_hashinfo et al and they require a hybrid approach.
>> The tables may be too big to construct a parallel data structure, we
>> don't want to hold off inserts or deletes while the expensive dump
>> is underway. Even though we can't build a shadow structure while
>> locking everybody else out, we still want to provide a way to somehow
>> achieve consistent information. I think that NLM_F_INTR with fallback
>> to restarting the dump is a good option and very easy to implement. In
>> that case, we want to lock out resize from dumping iterations but
>> still allow parallel insert/delete.
> 
> Well I guess Dave needs to make the call.  Do we want to allow
> lockless walks over the hash table or not?
> 
> Personally I don't think a linked list is that big a deal.  But then
> you guys were agonsing over a single pointer so who knows.

For netlink a linked list is no big deal, but for something like TCP
sockets it really is.
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