From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753117AbaJBQrO (ORCPT ); Thu, 2 Oct 2014 12:47:14 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:59285 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751789AbaJBQrN (ORCPT ); Thu, 2 Oct 2014 12:47:13 -0400 Date: Thu, 2 Oct 2014 09:46:57 -0700 From: Stephen Hemminger To: Nicolas Dichtel Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, ebiederm@xmission.com, akpm@linux-foundation.org, adobriyan@gmail.com, rui.xiang@huawei.com, viro@zeniv.linux.org.uk, oleg@redhat.com, gorcunov@openvz.org, kirill.shutemov@linux.intel.com, grant.likely@secretlab.ca, tytso@mit.edu, Thierry Herbelot Subject: Re: [RFC PATCH linux 2/2] fs/proc: use a hash table for the directory entries Message-ID: <20141002094657.1e28e027@urahara> In-Reply-To: <1412263501-6572-3-git-send-email-nicolas.dichtel@6wind.com> References: <20131003.150947.2179820478039260398.davem@davemloft.net> <1412263501-6572-1-git-send-email-nicolas.dichtel@6wind.com> <1412263501-6572-3-git-send-email-nicolas.dichtel@6wind.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2 Oct 2014 17:25:01 +0200 Nicolas Dichtel wrote: > From: Thierry Herbelot > > The current implementation for the directories in /proc is using a single > linked list. This is slow when handling directories with large numbers of > entries (eg netdevice-related entries when lots of tunnels are opened). > > This patch enables multiple linked lists. A hash based on the entry name is > used to select the linked list for one given entry. > > The speed creation of netdevices is faster as shorter linked lists must be > scanned when adding a new netdevice. > > Here are some numbers: > > dummy30000.batch contains 30 000 times 'link add type dummy'. > > Before the patch: > time ip -b dummy30000.batch > real 2m32.221s > user 0m0.380s > sys 2m30.610s > > After the patch: > time ip -b dummy30000.batch > real 1m57.190s > user 0m0.350s > sys 1m56.120s > > The single 'subdir' list head is replaced by a subdir hash table. The subdir > hash buckets are only allocated for directories. The number of hash buckets > is a compile-time parameter. > > For all functions which handle directory entries, an additional check on the > directory nature of the dir entry ensures that pde_hash_buckets was allocated. > This check was not needed as subdir was present for all dir entries, whether > actual directories or simple files. > > Signed-off-by: Thierry Herbelot > Signed-off-by: Nicolas Dichtel I think the speed up is a good idea and makes sense. It would be better to use exist hlist macros for hash table rather than open coding it.