From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mihai Maruseac Subject: Re: [PATCH] dev: use name hash for dev_seq_ops. Date: Mon, 10 Oct 2011 11:43:20 +0300 Message-ID: References: <1318000849-2531-1-git-send-email-mmaruseac@ixiacom.com> <20111007092445.4f097ed9@nehalam.linuxnetplumber.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: davem@davemloft.net, eric.dumazet@gmail.com, mirq-linux@rere.qmqm.pl, therbert@google.com, jpirko@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dbaluta@ixiacom.com, Mihai Maruseac To: Stephen Hemminger Return-path: In-Reply-To: <20111007092445.4f097ed9@nehalam.linuxnetplumber.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Oct 7, 2011 at 7:24 PM, Stephen Hemminger wrote: > On Fri, =A07 Oct 2011 18:20:49 +0300 > Mihai Maruseac wrote: > >> Instead of using the dev->next chain and trying to resync at each ca= ll to >> dev_seq_start, use this hash and store bucket number and bucket offs= et in >> seq->private field. >> >> As one can notice the improvement is of 1 order of magnitude. > > Good idea, > This will change the ordering of entries in /proc which may upset > some program, not a critical flaw but worth noting. > > Rather than recording the bucket and offset of last entry, another > alternative would be to just record the ifindex. > I tried to record the ifindex but I think that using it and dev_get_by_index can result in an infinite loop or a NULL dereferrence. If a device is removed and ifindex points to it we'll get a NULL from dev_get_by_index. Checking for NULL and calling again dev_get_by_index will end in an infinite loop at the end of the hlist. Augmenting the structure to also contain the number of indexes when the seq_file is opened returns to the current situation with two ints. Also, it is more prone to bugs caused by device removal while printing. --=20 Mihai