From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Dichtel Subject: Re: [RFC PATCH linux 2/2] fs/proc: use a hash table for the directory entries Date: Fri, 03 Oct 2014 15:10:51 +0200 Message-ID: <542EA05B.4010107@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> <20141002094657.1e28e027@urahara> Reply-To: nicolas.dichtel@6wind.com Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE 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 To: Stephen Hemminger Return-path: In-Reply-To: <20141002094657.1e28e027@urahara> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Le 02/10/2014 18:46, Stephen Hemminger a =E9crit : > 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 s= ingle >> linked list. This is slow when handling directories with large numbe= rs of >> entries (eg netdevice-related entries when lots of tunnels are opene= d). >> >> 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 m= ust 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. Th= e 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 chec= k 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 th= an > open coding it. > Right, I will rework this after looking at rbtree.