From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Laight Subject: RE: [PATCHv2 net-next 04/12] sctp: implement make_datafrag for sctp_stream_interleave Date: Fri, 8 Dec 2017 15:01:31 +0000 Message-ID: <67253734d93744a2b3b05d4a0bbe4a8f@AcuMS.aculab.com> References: <2ca21c61e82a44daa29226eac54a4950@AcuMS.aculab.com> <20171208145630.GE3328@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Cc: 'Xin Long' , network dev , "linux-sctp@vger.kernel.org" , Neil Horman , "davem@davemloft.net" To: 'Marcelo Ricardo Leitner' Return-path: Received: from smtp-out4.electric.net ([192.162.216.195]:58389 "EHLO smtp-out4.electric.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753718AbdLHPBR (ORCPT ); Fri, 8 Dec 2017 10:01:17 -0500 In-Reply-To: <20171208145630.GE3328@localhost.localdomain> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: From: Marcelo Ricardo Leitner > Sent: 08 December 2017 14:57 > > On Fri, Dec 08, 2017 at 02:06:04PM +0000, David Laight wrote: > > From: Xin Long > > > Sent: 08 December 2017 13:04 > > ... > > > @@ -264,8 +264,8 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc, > > > frag |= SCTP_DATA_SACK_IMM; > > > } > > > > > > - chunk = sctp_make_datafrag_empty(asoc, sinfo, len, frag, > > > - 0, GFP_KERNEL); > > > + chunk = asoc->stream.si->make_datafrag(asoc, sinfo, len, frag, > > > + GFP_KERNEL); > > > > I know that none of the sctp code is very optimised, but that indirect > > call is going to be horrid. > > Yeah.. but there is no way to avoid the double derreference > considering we only have the asoc pointer in there and we have to > reach the contents of the data chunk operations struct, and the .si > part is the same as 'stream' part as it's a constant offset. ... It isn't only the double indirect, the indirect call itself isn't 'fun'. I think there are other hot paths where you've replaced a sizeof() with a ?: clause. Caching the result might be much better. David