Return-path: Received: from py-out-1112.google.com ([64.233.166.178]:49347 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759430AbYGUCeD (ORCPT ); Sun, 20 Jul 2008 22:34:03 -0400 Received: by py-out-1112.google.com with SMTP id p76so911280pyb.10 for ; Sun, 20 Jul 2008 19:34:01 -0700 (PDT) Subject: Re: [PATCH 20/31]: pkt_sched: Perform bulk of qdisc destruction in RCU. From: jamal Reply-To: hadi@cyberus.ca To: Herbert Xu Cc: kaber@trash.net, davem@davemloft.net, netdev@vger.kernel.org, johannes@sipsolutions.net, linux-wireless@vger.kernel.org In-Reply-To: <20080721001119.GA6515@gondor.apana.org.au> References: <1216568119.4847.101.camel@localhost> <20080721001119.GA6515@gondor.apana.org.au> Content-Type: text/plain Date: Sun, 20 Jul 2008 22:33:57 -0400 Message-Id: <1216607637.4847.172.camel@localhost> (sfid-20080721_043411_008194_5F14D587) Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, 2008-21-07 at 08:11 +0800, Herbert Xu wrote: > This is exactly what I want to get rid of because otherwise even > if no index was specified we'll still do a hash insertion which > simply falls apart with a small hash table. Using a large hash > table on the other is bad for people who only have a few rules. True. But note: this is only during rule creation - once you create the rule (user space to kernel path), then no more hash table reference. Fast path has already a filter with actions attached, and is a mere pointer dereference. > We could do a dynamic table but so far I'm not convinced that > it's worth anybody's effort to implement :) If user<->kernel performance insertion/deletion is important, it is worth it. For example: Dave implemented dynamic hash tables on xfrm (voip setup time with ipsec is a metric used in the industry in that case) . The only operational problem i had with xfrm was lack of an upper bound of how large a table can grow; i would rather user space be told ENOMEM than continuing to grow in some cases (I actually implemented a patch which put a stop after a certain number of sad/spd - but i dont expect hugs if i was to post it;->). cheers, jamal