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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71CF6C43334 for ; Tue, 21 Jun 2022 01:27:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238710AbiFUB1F convert rfc822-to-8bit (ORCPT ); Mon, 20 Jun 2022 21:27:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45780 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230330AbiFUB1D (ORCPT ); Mon, 20 Jun 2022 21:27:03 -0400 Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 782D71900A for ; Mon, 20 Jun 2022 18:27:02 -0700 (PDT) Received: from omf13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 1CDB432FB4; Tue, 21 Jun 2022 01:27:01 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: joe@perches.com) by omf13.hostedemail.com (Postfix) with ESMTPA id 8A60120012; Tue, 21 Jun 2022 01:26:59 +0000 (UTC) Message-ID: Subject: Re: [PATCH v4 00/34] Printbufs - new data structure for building strings From: Joe Perches To: Kent Overstreet Cc: David Laight , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "pmladek@suse.com" , "rostedt@goodmis.org" , "enozhatsky@chromium.org" , "linux@rasmusvillemoes.dk" , "willy@infradead.org" Date: Mon, 20 Jun 2022 18:26:58 -0700 In-Reply-To: <20220621005752.ohiq5besmy3r5rjo@moria.home.lan> References: <20220620004233.3805-1-kent.overstreet@gmail.com> <0a5901f8460f452a89c9b0cda32fb833@AcuMS.aculab.com> <20220620150514.3tjy5dv7pv5frcwd@moria.home.lan> <53d77ae6101a0f24cfb694174d4c7699424c57e8.camel@perches.com> <20220621005752.ohiq5besmy3r5rjo@moria.home.lan> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8BIT User-Agent: Evolution 3.44.1-0ubuntu1 MIME-Version: 1.0 X-Stat-Signature: 6i9xmf7fozugzaj85ucgm93s6c5syqtf X-Rspamd-Server: rspamout04 X-Rspamd-Queue-Id: 8A60120012 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Session-ID: U2FsdGVkX1+6laJhvDVSxjllgACLhEHrhgVyrTNCaWA= X-HE-Tag: 1655774819-286916 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2022-06-20 at 20:57 -0400, Kent Overstreet wrote: > On Mon, Jun 20, 2022 at 05:38:51PM -0700, Joe Perches wrote: > > On Mon, 2022-06-20 at 11:07 -0400, Kent Overstreet wrote: > > > On Mon, Jun 20, 2022 at 04:19:31AM +0000, David Laight wrote: > > > > I really think that is a bad idea. > > > > printk() already uses a lot of stack, anything doing a recursive > > > > call is just making that worse. > > > > Especially since these calls can often be in error paths > > > > which are not often tested and can already be on deep stacks. > > > > > > We went over this before - this patch series drastically reduces stack usage of > > > sprintf by eliminating a bunch of stack allocated buffers. Do try to keep up... > > > > I generally agree with David. > > > > I think Kent has not provided data that this actually _reduces_ > > stack usage. > > I think the people who are comfortable with reading C can discern that when > large stack allocated character arrays are deleted, frame size and stack usage > go down. I am very comfortable reading C. You have not provided any data.