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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 36BE1C4727C for ; Wed, 30 Sep 2020 14:32:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05BDA20789 for ; Wed, 30 Sep 2020 14:32:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730460AbgI3OcT convert rfc822-to-8bit (ORCPT ); Wed, 30 Sep 2020 10:32:19 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:54023 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728149AbgI3OcT (ORCPT ); Wed, 30 Sep 2020 10:32:19 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-195-PQuEQoKvMGmaHF5ETfZwSQ-2; Wed, 30 Sep 2020 15:32:15 +0100 X-MC-Unique: PQuEQoKvMGmaHF5ETfZwSQ-2 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Wed, 30 Sep 2020 15:32:12 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Wed, 30 Sep 2020 15:32:12 +0100 From: David Laight To: 'Steven Rostedt' , Rasmus Villemoes CC: Petr Mladek , John Ogness , Sergey Senozhatsky , Sergey Senozhatsky , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH printk 3/5] printk: use buffer pool for sprint buffers Thread-Topic: [PATCH printk 3/5] printk: use buffer pool for sprint buffers Thread-Index: AQHWly6i3uftD0MwYEu+n/WNbQR9JamBPhZA Date: Wed, 30 Sep 2020 14:32:12 +0000 Message-ID: <3d6c42b0734a4713b45647415a51bcc1@AcuMS.aculab.com> References: <20200922153816.5883-1-john.ogness@linutronix.de> <20200922153816.5883-4-john.ogness@linutronix.de> <20200923151129.GC6442@alley> <2c95c16b-03e7-eadd-d3af-bedc6b0b471e@prevas.dk> <20200925082822.GL29288@alley> <4e36f308-a435-f9c1-2d4f-362e797c764e@prevas.dk> <20200930093552.3684aee1@gandalf.local.home> In-Reply-To: <20200930093552.3684aee1@gandalf.local.home> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt > Sent: 30 September 2020 14:36 > > On Wed, 30 Sep 2020 10:06:24 +0200 > Rasmus Villemoes wrote: > > > True. But remember that printk is called from _everywhere_, with all > > sorts of locks held and/or preemption disabled or whatnot, and every > > cycle spent in printk makes those windows wider. Doubling the cost of > > every single printk by unconditionally doing vsnprintf() twice is a bad > > idea. > > But the console output is usually magnitudes more expensive than the > vsnprintf(), would doing it twice really make a difference? Are there any strange %pX modifiers that do anything really horrid? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)