From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AB36C43603 for ; Thu, 5 Dec 2019 14:06:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1D53B2464D for ; Thu, 5 Dec 2019 14:06:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729534AbfLEOGZ (ORCPT ); Thu, 5 Dec 2019 09:06:25 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:59160 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729236AbfLEOGY (ORCPT ); Thu, 5 Dec 2019 09:06:24 -0500 Received: from localhost ([127.0.0.1] helo=vostro.local) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1icrlU-00030b-96; Thu, 05 Dec 2019 15:05:56 +0100 From: John Ogness To: Prarit Bhargava Cc: linux-kernel@vger.kernel.org, andrea.parri@amarulasolutions.com, brendanhiggins@google.com, gregkh@linuxfoundation.org, kexec@lists.infradead.org, peterz@infradead.org, pmladek@suse.com, rostedt@goodmis.org, sergey.senozhatsky@gmail.com, sergey.senozhatsky.work@gmail.com, tglx@linutronix.de, torvalds@linux-foundation.org Subject: Re: [RFC PATCH v5 0/3] printk: new ringbuffer implementation References: <20191128015235.12940-1-john.ogness@linutronix.de> <20191205134652.12631-1-prarit@redhat.com> Date: Thu, 05 Dec 2019 15:05:54 +0100 In-Reply-To: <20191205134652.12631-1-prarit@redhat.com> (Prarit Bhargava's message of "Thu, 5 Dec 2019 08:46:52 -0500") Message-ID: <87zhg6zx31.fsf@linutronix.de> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Prarit, On 2019-12-05, Prarit Bhargava wrote: > Based on the comments there is going to be a v6 but in any case I am > starting testing of this patchset on several large core systems across > multiple architectures (x86_64, ARM64, s390, ppc64le). Some of those > systems are known to fail boot due to the large amount of printk output so > it will be good to see if these changes resolve those issues. Right now the patches only include the ringbuffer as a separate entity with a test module. So they do not yet have any effect on printk. If you apply the patches and then build the "modules" target, you will have a new test_prb.ko module. Loading that module will start some heavy testing of the ringbuffer. As long as the testing is successful, the module will keep testing. During this time the machine will be very slow, but should still respond. The test can be stopped by unloading the module. If the test stops on its own, then a problem was found. The output of the test is put into the ftrace buffer. It would be nice if you could run the test module on some fat machines, at least for a few minutes to see if anything explodes. ARM64 and ppc64le will probably be the most interesting, due to memory barrier testing. Otherwise I will definitely be reaching out to you when we are ready to perform actual printk testing with the newly agreed up semantics (lockless, per-console printing threads, synchronous panic consoles). Thanks for your help with this. John Ogness