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Date: Tue, 24 Feb 2015 10:46:04 +0000 From: David Laight <David.Laight@...LAB.COM> To: 'Patrick McHardy' <kaber@...sh.net>, Thomas Graf <tgraf@...g.ch> CC: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, David Miller <davem@...emloft.net>, "josh@...htriplett.org" <josh@...htriplett.org>, "alexei.starovoitov@...il.com" <alexei.starovoitov@...il.com>, "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>, "ying.xue@...driver.com" <ying.xue@...driver.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org> Subject: RE: Ottawa and slow hash-table resize From: Patrick McHardy > On 24.02, Thomas Graf wrote: > > On 02/23/15 at 03:06pm, Paul E. McKenney wrote: > > > On Mon, Feb 23, 2015 at 05:32:52PM -0500, David Miller wrote: > > > > I just did a quick scan of all code paths that do inserts into an > > > > rhashtable, and it seems like all of them can easily block. So why > > > > don't we do that? Make inserts sleep on an rhashtable expansion > > > > waitq. > > > > > > > > There could even be a counter of pending inserts, so the expander can > > > > decide to expand further before waking the inserting threads up. > > > > > > Should be reasonably simple, and certainly seems worth a try! > > > > Agreed. Definitely desirable for nft_hash. I like the pending counter > > idea. I'm experimenting with various ideas on blocking inserts for > > Netlink. Blocking too long might open DoS vectors as one app could > > easily delay the creation of sockets for other applications. > > Regarding nft_hash, blocking in the netlink path certainly seems fine, > but we will soon also have inserts from the packet processing path, > where we obviously can't block. Why not an option to do a synchronous 'expand on insert' for codepaths that can block? David -- 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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