From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Graf Subject: Re: Ottawa and slow hash-table resize Date: Tue, 24 Feb 2015 08:37:14 +0000 Message-ID: <20150224083714.GB17306@casper.infradead.org> References: <20150223191201.GA4355@cloud> <20150223210358.GB806@casper.infradead.org> <20150223215248.GA15405@linux.vnet.ibm.com> <20150223.173252.397503088215638994.davem@davemloft.net> <20150223230619.GD15405@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , josh@joshtriplett.org, alexei.starovoitov@gmail.com, herbert@gondor.apana.org.au, kaber@trash.net, ying.xue@windriver.com, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org To: "Paul E. McKenney" Return-path: Received: from casper.infradead.org ([85.118.1.10]:44226 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750748AbbBXIhT (ORCPT ); Tue, 24 Feb 2015 03:37:19 -0500 Content-Disposition: inline In-Reply-To: <20150223230619.GD15405@linux.vnet.ibm.com> Sender: netfilter-devel-owner@vger.kernel.org List-ID: 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.