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Date: Fri, 16 Jan 2015 23:34:14 +0000 From: Thomas Graf <tgraf@...g.ch> To: Patrick McHardy <kaber@...sh.net> Cc: David Laight <David.Laight@...LAB.COM>, "davem@...emloft.net" <davem@...emloft.net>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>, "paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>, "edumazet@...gle.com" <edumazet@...gle.com>, "john.r.fastabend@...el.com" <john.r.fastabend@...el.com>, "josh@...htriplett.org" <josh@...htriplett.org>, "netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org> Subject: Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred expansion/shrinking On 01/16/15 at 10:07pm, Patrick McHardy wrote: > I'm afraid that's not good enough. The resize operation is deferred, > so even if userspace does not perform an operation after starting > the dump, the hash might change. > > We can obviously work around that by incrementing a generation > counter in rhashtable. The main problem I see is that with something > very actively changing the ruleset, we might never complete a dump. Right, I suggest adding a function pointer to rhashtable_params, which when set, is called on resize so users can bump their own sequence counter on resize. > Dumps are usually rare, I think its preferrable to defer rehashing. Resize operations should be *really* rare as well unless you start with really small hash table sizes and constantly add/remove at the watermark. Re-dumping on insert/remove is a different story of course. Do you care about missed insert/removals for dumps? If not we can do the sequence number consistency checking for resizing only. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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