From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751481AbcGMQxq (ORCPT ); Wed, 13 Jul 2016 12:53:46 -0400 Received: from www62.your-server.de ([213.133.104.62]:52863 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750959AbcGMQxi (ORCPT ); Wed, 13 Jul 2016 12:53:38 -0400 Message-ID: <57867207.3010706@iogearbox.net> Date: Wed, 13 Jul 2016 18:53:27 +0200 From: Daniel Borkmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Peter Zijlstra CC: davem@davemloft.net, alexei.starovoitov@gmail.com, tgraf@suug.ch, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 1/3] perf, events: add non-linear data support for raw records References: <20160713134231.GT30154@twins.programming.kicks-ass.net> <57864B77.9090105@iogearbox.net> <20160713164007.GV30154@twins.programming.kicks-ass.net> In-Reply-To: <20160713164007.GV30154@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/13/2016 06:40 PM, Peter Zijlstra wrote: > On Wed, Jul 13, 2016 at 04:08:55PM +0200, Daniel Borkmann wrote: >> On 07/13/2016 03:42 PM, Peter Zijlstra wrote: >>> >>> Ok so the nonlinear thing was it doing _two_ copies, one the regular >>> __output_copy() on raw->data and second the optional fragment thingy >>> using __output_custom(). >>> >>> Would something like this work instead? >>> >>> It does the nonlinear thing and the custom copy function thing but >>> allows more than 2 fragments and allows each fragment to have a custom >>> copy. >>> >>> It doesn't look obviously more expensive; it has the one ->copy branch >>> extra, but then it doesn't recompute the sizes. >> >> Yes, that would work as well on a quick glance with diff just a bit >> bigger, but more generic this way. Do you want me to adapt this into >> the first patch? > > Please. > >> One question below: >> > >>> - u64 zero = 0; > >>> - if (real_size - raw_size) >>> - __output_copy(handle, &zero, real_size - raw_size); > >> We still need the zero padding here from above with the computed >> raw->size, right? > > Ah, yes, we need some __output*() in order to advance the handle offset. > We don't _need_ to copy the 0s, but I doubt __output_skip() is much > cheaper for these 1-3 bytes worth of data; we've already touched that > line anyway. Okay, thanks for your input! I'll respin then.