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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 808A2C433EF for ; Tue, 21 Jun 2022 00:38:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 77EE56B0071; Mon, 20 Jun 2022 20:38:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 705596B0073; Mon, 20 Jun 2022 20:38:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5A6686B0074; Mon, 20 Jun 2022 20:38:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 45EF26B0071 for ; Mon, 20 Jun 2022 20:38:56 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 12B6460512 for ; Tue, 21 Jun 2022 00:38:56 +0000 (UTC) X-FDA: 79600383072.22.4EBA335 Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by imf08.hostedemail.com (Postfix) with ESMTP id 978F11600A7 for ; Tue, 21 Jun 2022 00:38:55 +0000 (UTC) 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: quoted-printable User-Agent: Evolution 3.44.1-0ubuntu1 MIME-Version: 1.0 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Session-ID: U2FsdGVkX18iuMOlb5rJsZQ4wQ5Qfk4CeiXDod72ZqY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655771935; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=P5q1FoJdD0BHVmsF1rdfwiHRukko5pMoJG9pkAWGui0=; b=xNRLUzRkmDEvd9vE6JKWGlgUkrn+vm8rTImatugeHs0BNhCPW850uo7U/d6r8GcnkYgii4 TZKoXCkXo+qBfHVJ46B6JAJALSVl48xjkbiBfrOqQ6t+yfZ5kdtCfefbFx4i1Mi12YVIHh fVkQvidwJkgIJWiwGVSGqj+pKJ6maUE= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; spf=none (imf08.hostedemail.com: domain of joe@perches.com has no SPF policy when checking 216.40.44.14) smtp.mailfrom=joe@perches.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655771935; a=rsa-sha256; cv=none; b=HgsIasixLcM3jHVkeTfje/ZBBmi0lHHJ+XYlaI33km/peCHMKdjcoLUAiXyMpmKbesmrkY JnJZskD/8BjkeueQyv6cA45Z0+OeGdpk34SKDm7J+8e9NQc0WXaVD3js9s997ZyaS3P3o+ AKCCAPcxLOOQ26DQuNKDjCGI9yqhNlg= X-HE-Tag-Orig: 1655771932-377534 X-Stat-Signature: kergigzb7c1fs6w144t5qkfk813n7x4i X-Rspamd-Queue-Id: 978F11600A7 X-Rspamd-Server: rspam11 X-Rspam-User: Authentication-Results: imf08.hostedemail.com; dkim=none; spf=none (imf08.hostedemail.com: domain of joe@perches.com has no SPF policy when checking 216.40.44.14) smtp.mailfrom=joe@perches.com; dmarc=none X-HE-Tag: 1655771935-58855 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. >=20 > We went over this before - this patch series drastically reduces stack us= age 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.