From mboxrd@z Thu Jan 1 00:00:00 1970 From: marcelo.leitner@gmail.com Subject: Re: [PATCH net-next 0/2] pskb_extract() helper function. Date: Fri, 22 Apr 2016 20:23:01 -0300 Message-ID: <20160422232301.GA1594@localhost.localdomain> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, rds-devel@oss.oracle.com, santosh.shilimkar@oracle.com, davem@davemloft.net, eric.dumazet@gmail.com To: Sowmini Varadhan Return-path: Received: from mx1.redhat.com ([209.132.183.28]:48268 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753360AbcDVXXG (ORCPT ); Fri, 22 Apr 2016 19:23:06 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Apr 20, 2016 at 03:17:40AM -0700, Sowmini Varadhan wrote: > This patchset follows up on the discussion in > https://www.mail-archive.com/netdev@vger.kernel.org/msg105090.html > > For RDS-TCP, we have to deal with the full gamut of > nonlinear sk_buffs, including all the frag_list variants. > Also, the parent skb has to remain unchanged, while the clone > is queued for Rx on the PF_RDS socket. > > Patch 1 of this patchset adds a pskb_extract() function that > does all this without the redundant memcpy's in pskb_expand_head() > and __pskb_pull_tail(). I applied this patchset and updated SCTP to also use it for data chunks. My tests results were very similar to what I had without it. Varying to better or worse, tending worse. Thing is, SCTP always works on linearized skbs as it can't crawl on fragments, so those clone/trim operations are just offset adjusts regarding the data, and it's shared. With pskb_extract, it implies in a new memory allocation and a copy, even in this best case, so for SCTP, for now, it's actually a drawback I'm afraid. Marcelo