From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422681AbcIZQN1 (ORCPT ); Mon, 26 Sep 2016 12:13:27 -0400 Received: from mga01.intel.com ([192.55.52.88]:34226 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161623AbcIZQNY (ORCPT ); Mon, 26 Sep 2016 12:13:24 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,400,1470726000"; d="scan'208";a="1046080105" From: Alexander Shishkin To: Peter Zijlstra Cc: Andi Kleen , Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , tglx@linutronix.de Subject: Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation In-Reply-To: <20160926090354.GK5012@twins.programming.kicks-ass.net> References: <20160923112726.5890-1-alexander.shishkin@linux.intel.com> <20160923112726.5890-2-alexander.shishkin@linux.intel.com> <20160923121403.GC5012@twins.programming.kicks-ass.net> <20160923172615.GU3078@tassilo.jf.intel.com> <20160923202830.GQ5008@twins.programming.kicks-ass.net> <878tufrrqb.fsf@ashishki-desk.ger.corp.intel.com> <20160926090354.GK5012@twins.programming.kicks-ass.net> User-Agent: Notmuch/0.22.1 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Mon, 26 Sep 2016 19:13:20 +0300 Message-ID: <87oa3ar65b.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Mon, Sep 26, 2016 at 11:27:08AM +0300, Alexander Shishkin wrote: >> Peter Zijlstra writes: >> >> > Well, we could 'force' inject a VMA into the process's address space, we >> > do that for a few other things as well. It also makes for less >> > exceptions with the actual core dumping. >> >> Threads then will end up with the same buffer (through sharing the mm), >> but they can't really share trace buffers. >> >> Also, system core dump is still a problem. > > Hurm, true on both counts. OTOH, system core dump buffers don't need inheritance or memlock accounting. >> Or we can have per-cpu buffers for all user's tasks, record where each >> task starts and ends in each buffer and cut out only bits relevant to >> the task(s) that dump core. > > Which gets you the problem that when a task dumps core there might not > be any state in the buffer, because the previous task flushed it all out > :/ And also won't work with PMUs that don't generate PMIs, like ETMs. Regards, -- Alex