From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752338Ab3LSLR5 (ORCPT ); Thu, 19 Dec 2013 06:17:57 -0500 Received: from mga09.intel.com ([134.134.136.24]:64632 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751394Ab3LSLR4 (ORCPT ); Thu, 19 Dec 2013 06:17:56 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,512,1384329600"; d="scan'208";a="427155295" From: Alexander Shishkin To: Peter Zijlstra Cc: Arnaldo Carvalho de Melo , Ingo Molnar , linux-kernel@vger.kernel.org, David Ahern , Frederic Weisbecker , Jiri Olsa , Mike Galbraith , Namhyung Kim , Paul Mackerras , Stephane Eranian , Andi Kleen Subject: Re: [PATCH v0 04/71] itrace: Infrastructure for instruction flow tracing units In-Reply-To: <20131219103134.GD30183@twins.programming.kicks-ass.net> References: <1386765443-26966-1-git-send-email-alexander.shishkin@linux.intel.com> <1386765443-26966-5-git-send-email-alexander.shishkin@linux.intel.com> <20131217161126.GL13532@twins.programming.kicks-ass.net> <8761qmthr6.fsf@ashishki-desk.ger.corp.intel.com> <20131218133439.GR21999@twins.programming.kicks-ass.net> <8738lqtg0v.fsf@ashishki-desk.ger.corp.intel.com> <20131218141125.GT21999@twins.programming.kicks-ass.net> <87zjnys0gj.fsf@ashishki-desk.ger.corp.intel.com> <20131218150900.GU21999@twins.programming.kicks-ass.net> <87wqj1s2d3.fsf@ashishki-desk.ger.corp.intel.com> <20131219103134.GD30183@twins.programming.kicks-ass.net> User-Agent: Notmuch/0.15.2+182~gd0bd88f (http://notmuchmail.org) Emacs/23.4.1 (x86_64-pc-linux-gnu) Date: Thu, 19 Dec 2013 13:17:51 +0200 Message-ID: <87ob4drsww.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Thu, Dec 19, 2013 at 09:53:44AM +0200, Alexander Shishkin wrote: >> Yes and some implementations of PT have the same issue, but you can do a >> sufficiently large high order allocation and map it to userspace and >> still no copying (or parsing/decoding) in kernel space required. > > What's sufficiently large? The largest we could possibly allocate is > something like 4k^11 which is 8M or so. That's not all that big given > you keep saying it generates in the order of 100 MB/s. One chunk is 8M. You can have as many as the buddy allocator permits you to have. When you get a PMI, you simply switch one chunk for another and on the tracing goes. > Also, 'some implementations', that sounds like a fail right there. Why > are there already different implementations, and some which such stupid > design, of something this new? > > How about just saying NO to the ones that requires physically contiguous > allocations? No reason to leave those out, because they are still extremely useful for tracing and fit perfectly fine in a model with two buffers. Regards, -- Alex