Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757410Ab2EWIV1 (ORCPT ); Wed, 23 May 2012 04:21:27 -0400 Received: from merlin.infradead.org ([205.233.59.134]:33461 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756964Ab2EWIVY convert rfc822-to-8bit (ORCPT ); Wed, 23 May 2012 04:21:24 -0400 Message-ID: <1337761273.9698.60.camel@twins> Subject: Re: [PATCH v2 4/5] perf record: add meta-data support for pipe-mode From: Peter Zijlstra To: Stephane Eranian Cc: Arnaldo Carvalho de Melo , David Ahern , linux-kernel@vger.kernel.org, mingo@elte.hu Date: Wed, 23 May 2012 10:21:13 +0200 In-Reply-To: References: <1337081295-10303-1-git-send-email-eranian@google.com> <1337081295-10303-5-git-send-email-eranian@google.com> <4FB32032.3000509@gmail.com> <4FB67DE5.8050000@gmail.com> <20120518171911.GH2636@infradead.org> <1337708035.9698.44.camel@twins> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1177 Lines: 25 On Tue, 2012-05-22 at 19:51 +0200, Stephane Eranian wrote: > The problem is that the headers as they are written to the file need > seeking in the file to update the offset table. That is NOT possible when > you operate in pipe mode. I know that, I said as much. But it is quite possible to multiplex streams without the need for seeking, look at these MKV containers that contain video, multiple-audio and multiple-subtitle tracks. The fact is, whomever wrote that pipe mode took a bonghit before touching the keyboard. They didn't even ask if we could reserve a range for userspace events, let alone consider if it was a good idea to begin with. If we ever manage to get splice() working you can't keep that pipe mode working anyway. Pushing everything over a single stream isn't a scalable solution anyway in the same way that writing everything into the one file isn't the best thing and would ideally be replaced as well. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/