From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx2.suse.de ([195.135.220.15]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqzJf-0006L7-C1 for kexec@lists.infradead.org; Thu, 02 Jul 2020 13:31:52 +0000 Date: Thu, 2 Jul 2020 15:27:58 +0200 From: Petr Mladek Subject: Re: buffer allocation: was: [PATCH v3 3/3] printk: use the lockless ringbuffer Message-ID: <20200702132758.GD14288@alley> References: <20200618144919.9806-1-john.ogness@linutronix.de> <20200618144919.9806-4-john.ogness@linutronix.de> <20200625082838.GF6156@alley> <87sgeh3m5j.fsf@jogness.linutronix.de> <20200629140445.GK6156@alley> <87ftad8rh4.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87ftad8rh4.fsf@jogness.linutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: John Ogness Cc: Andrea Parri , Sergey Senozhatsky , Paul McKenney , Peter Zijlstra , Greg Kroah-Hartman , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Steven Rostedt , Sergey Senozhatsky , Thomas Gleixner , Linus Torvalds On Mon 2020-06-29 23:57:59, John Ogness wrote: > On 2020-06-29, Petr Mladek wrote: > >> @@ @@ void __init setup_log_buf(int early) > >> + prb_init(&printk_rb_dynamic, > >> + new_log_buf, order_base_2(new_log_buf_len), > >> + new_dict_buf, order_base_2(new_log_buf_len), > >> + new_descs, order_base_2(new_descs_count)); > > > > order_base_2() is safe. But the result might be tat some allocated > > space is not used. > > > > I would prefer to make sure that new_log_buf_len is rounded, e.g. > > by roundup_pow_of_two(), at the beginning of the function. Then we > > could use ilog2() here. > > new_log_buf_len can only be set within log_buf_len_update(), and it > is already doing exactly what you want: > > if (size) > size = roundup_pow_of_two(size); > if (size > log_buf_len) > new_log_buf_len = (unsigned long)size; I know. I though about repeating this in setup_log_bug() to make it error proof. But it is not really needed. I do not resist on it. > I can switch to ilog2() instead of the more conservative order_base_2(). Yes, please change it to ilog2(). Best Regards, Petr _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec 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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7D03FC433DF for ; Thu, 2 Jul 2020 13:31:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58DDF2088E for ; Thu, 2 Jul 2020 13:31:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729257AbgGBNbv (ORCPT ); Thu, 2 Jul 2020 09:31:51 -0400 Received: from mx2.suse.de ([195.135.220.15]:36804 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729047AbgGBNbv (ORCPT ); Thu, 2 Jul 2020 09:31:51 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6A47FBC6A; Thu, 2 Jul 2020 13:31:50 +0000 (UTC) Date: Thu, 2 Jul 2020 15:27:58 +0200 From: Petr Mladek To: John Ogness Cc: Peter Zijlstra , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Paul McKenney , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: buffer allocation: was: [PATCH v3 3/3] printk: use the lockless ringbuffer Message-ID: <20200702132758.GD14288@alley> References: <20200618144919.9806-1-john.ogness@linutronix.de> <20200618144919.9806-4-john.ogness@linutronix.de> <20200625082838.GF6156@alley> <87sgeh3m5j.fsf@jogness.linutronix.de> <20200629140445.GK6156@alley> <87ftad8rh4.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87ftad8rh4.fsf@jogness.linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2020-06-29 23:57:59, John Ogness wrote: > On 2020-06-29, Petr Mladek wrote: > >> @@ @@ void __init setup_log_buf(int early) > >> + prb_init(&printk_rb_dynamic, > >> + new_log_buf, order_base_2(new_log_buf_len), > >> + new_dict_buf, order_base_2(new_log_buf_len), > >> + new_descs, order_base_2(new_descs_count)); > > > > order_base_2() is safe. But the result might be tat some allocated > > space is not used. > > > > I would prefer to make sure that new_log_buf_len is rounded, e.g. > > by roundup_pow_of_two(), at the beginning of the function. Then we > > could use ilog2() here. > > new_log_buf_len can only be set within log_buf_len_update(), and it > is already doing exactly what you want: > > if (size) > size = roundup_pow_of_two(size); > if (size > log_buf_len) > new_log_buf_len = (unsigned long)size; I know. I though about repeating this in setup_log_bug() to make it error proof. But it is not really needed. I do not resist on it. > I can switch to ilog2() instead of the more conservative order_base_2(). Yes, please change it to ilog2(). Best Regards, Petr