Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754062AbaFMWGW (ORCPT ); Fri, 13 Jun 2014 18:06:22 -0400 Received: from mail-lb0-f173.google.com ([209.85.217.173]:56288 "EHLO mail-lb0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753926AbaFMWGU (ORCPT ); Fri, 13 Jun 2014 18:06:20 -0400 MIME-Version: 1.0 In-Reply-To: <1402695712.27369.10.camel@buesod1.americas.hpqcorp.net> References: <1402684097-5731-1-git-send-email-mcgrof@do-not-panic.com> <1402695712.27369.10.camel@buesod1.americas.hpqcorp.net> From: "Luis R. Rodriguez" Date: Fri, 13 Jun 2014 15:05:59 -0700 X-Google-Sender-Auth: YqL-Tpkaydwdd-q9iVdmKJzYDW8 Message-ID: Subject: Re: [PATCH v3] printk: allow increasing the ring buffer depending on the number of CPUs To: Davidlohr Bueso Cc: hpa@linux.intel.com, Andrew Morton , "linux-kernel@vger.kernel.org" , Michal Hocko , Petr Mladek , Joe Perches , Arun KS , Kees Cook , Chris Metcalf Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 13, 2014 at 2:41 PM, Davidlohr Bueso wrote: > On Fri, 2014-06-13 at 11:28 -0700, Luis R. Rodriguez wrote: >> + /* >> + * If you set log_buf_len=n kernel parameter LOG_CPU_MIN_BUF_SHIFT will >> + * be ignored. LOG_CPU_MIN_BUF_SHIFT is a proactive measure for large >> + * systems. With a LOG_BUF_SHIFT of 18 and LOG_CPU_MIN_BUF_SHIFT 12 at >> + * we'd require more than 64 CPUs to trigger an increase from the >> + * default. >> + */ >> + if (!new_log_buf_len && (cpu_extra > __LOG_BUF_LEN / 2)) > ^ that ! looks wrong. That check is there so that we ignore the cpu_extra stuff if the kernel parameter was passed, given that in that case new_log_buf_len would be set. > We should be checking for log_buf_len set instead. When log_buf_len=n is set as a kernel parameter log_buf_len_setup() will set new_log_buf_len to something, the sanity test to not update the ring buffer unless the value passed is greater than the default value is checked by log_buf_len_setup(). >> + new_log_buf_len = __LOG_BUF_LEN + cpu_extra; > > You could also move the whole thing below the return statement, that way > we can avoid double checking new_log_buf_len. Otherwise looks kinda > weird. If we did we'd be forcing the kernel parameter to be used to enable this functionality, but we don't want that. Luis -- 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/