From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [PATCH] Reduce overhead in find_domain_by_id() [0/2] Date: Wed, 06 Dec 2006 12:12:41 +0000 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "Apparao, Padmashree K" , Keir Fraser , "Santos, Jose Renato G" , xen-devel@lists.xensource.com Cc: Yoshio Turner , Jose Renato Santos , G John Janakiraman List-Id: xen-devel@lists.xenproject.org Okay, sounds good. I don't want the whole Linux RCU mechanism in Xen particularly. Linux may well need the complexity because it leans on RCU quite heavily these days, but Xen will do so a whole lot less I'm sure and something much simpler should suffice. I'll look into this -- the patches you sent provide a good starting point, thanks! -- Keir On 6/12/06 11:52, "Apparao, Padmashree K" wrote: > Keir, > > Earlier this summer I had done some experiments with Iperf and found > that find_domain_id was consuming 7% of cpu while do_grant_table_op was > consuming 10.5%. A quick fix to figure what the upper bound of > performance gain was to remove the hash table lookups in > find_domain_by_id and we saw a 12% improvement in perf receive > performance. > The results of these finding were published in our paper at VTDC. > In that paper we also discuss how the inter vm communication by grant > tables was consuming a considerable amount of time and what could be > possibly done to optimize. > > I will send the paper is a separate note to you and Renato. > > Thanks > - Padma > > > > -----Original Message----- > From: xen-devel-bounces@lists.xensource.com > [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Keir Fraser > Sent: Wednesday, December 06, 2006 12:44 AM > To: Santos, Jose Renato G; xen-devel@lists.xensource.com > Cc: Yoshio Turner; Jose Renato Santos; G John Janakiraman > Subject: Re: [Xen-devel] [PATCH] Reduce overhead in find_domain_by_id() > [0/2] > > On 6/12/06 1:35 am, "Santos, Jose Renato G" > wrote: > >> >> This is a set of patches to improve performance of > find_domain_by_id(). >> find_domain_by_id shows up high in profiles for network I/O intensive >> workloads. >> Most of the cost for this function comes from 3 main functions (of >> aproximate equal costs): 1)read_lock(), 2)read_unlock() and >> 3)get_domain(). >> These patches replace the lock used for accessing domain_list and >> domain_hash with a lock free RCU scheme. Experiments confirm that the >> cost of find_domain_by_id() is in fact reduced by 2/3. >> The patches apply cleanly to changeset 12732. > > Do you have numbers for performance improvement on a macro benchmark? > > -- Keir > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel