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 AFA2DC433EF for ; Tue, 21 Jun 2022 00:39:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243269AbiFUAi7 convert rfc822-to-8bit (ORCPT ); Mon, 20 Jun 2022 20:38:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235324AbiFUAi5 (ORCPT ); Mon, 20 Jun 2022 20:38:57 -0400 Received: from relay3.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A61510FE8 for ; Mon, 20 Jun 2022 17:38:56 -0700 (PDT) Received: from omf02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id B538D20FDD; Tue, 21 Jun 2022 00:38:53 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: joe@perches.com) by omf02.hostedemail.com (Postfix) with ESMTPA id 254A08000A; Tue, 21 Jun 2022 00:38:52 +0000 (UTC) Message-ID: <53d77ae6101a0f24cfb694174d4c7699424c57e8.camel@perches.com> Subject: Re: [PATCH v4 00/34] Printbufs - new data structure for building strings From: Joe Perches To: Kent Overstreet , David Laight Cc: "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 17:38:51 -0700 In-Reply-To: <20220620150514.3tjy5dv7pv5frcwd@moria.home.lan> References: <20220620004233.3805-1-kent.overstreet@gmail.com> <0a5901f8460f452a89c9b0cda32fb833@AcuMS.aculab.com> <20220620150514.3tjy5dv7pv5frcwd@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: 4q1qktg797qyt7kwq1opekn7fu3or1wu X-Rspamd-Server: rspamout06 X-Rspamd-Queue-Id: 254A08000A X-Session-Marker: 6A6F6540706572636865732E636F6D X-Session-ID: U2FsdGVkX18iuMOlb5rJsZQ4wQ5Qfk4CeiXDod72ZqY= X-HE-Tag: 1655771932-377534 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Converting stack variables to call stack frames does not necessarily reduce overall stack usage when the stack frame plus any locally used stack in the called function is added together.