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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 A771AC433B4 for ; Fri, 2 Apr 2021 14:42:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5283B60200 for ; Fri, 2 Apr 2021 14:42:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5283B60200 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DC6B36B0072; Fri, 2 Apr 2021 10:42:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D776C6B0073; Fri, 2 Apr 2021 10:42:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C17F46B0074; Fri, 2 Apr 2021 10:42:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0230.hostedemail.com [216.40.44.230]) by kanga.kvack.org (Postfix) with ESMTP id A2A7A6B0072 for ; Fri, 2 Apr 2021 10:42:57 -0400 (EDT) Received: from smtpin36.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 5EA4611905 for ; Fri, 2 Apr 2021 14:42:57 +0000 (UTC) X-FDA: 77987693994.36.8353CC2 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf19.hostedemail.com (Postfix) with ESMTP id C219390009F4 for ; Fri, 2 Apr 2021 14:42:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Bw7ISwmFV0i1SzllnQ2AVohh/lybr5ParuExcTXKJKg=; b=LAQSsv5uOnx0JrA0LDyFhl9r+2 5l2kW1mnPfTNrIY4ns6ovHqeN6VeP2uFLLgkTCXr3I41UD5qywqrdoMfLZ47Rg8Arl0o+ADTXKhRN AznFUAAgCp4RoJ3qyGytoRiDcpBwOM093dTv/gz2NoocS+BFielEdSJnpP9NMF4NYP/I8vyvcFcKy pN3/tYJgbUbiQRqDFLtsbnoB8SWTbjgtkT1uRrtIOM2dmy+Wqvv5d/ObsRsI28NQiIalmGXkVTW0A t+AX7MpwM3pAIDWv/ScOqj4twGYgbx4v90qeyRissqF1s10M6ZESK+0WUyAUXG+RnwUXz6BVYaXBX EQtk5nwg==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lSKzA-007kKL-30; Fri, 02 Apr 2021 14:42:21 +0000 Date: Fri, 2 Apr 2021 15:41:20 +0100 From: Matthew Wilcox To: Greg KH Cc: yangerkun , stable@vger.kernel.org, vbabka@suse.cz, linux-mm@kvack.org, open-iscsi@googlegroups.com, cleech@redhat.com, "zhangyi (F)" , Kefeng Wang , liuyongqiang13@huawei.com, "Zhengyejian (Zetta)" , Yang Yingliang , chenzhou10@huawei.com Subject: Re: [QUESTION] WARNNING after 3d8e2128f26a ("sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output") Message-ID: <20210402144120.GO351017@casper.infradead.org> References: <5837f5d9-2235-3ac2-f3f2-712e6cf4da5c@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: nrug86iwacpedsdhru1na56xafa8d6tr X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C219390009F4 Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf19; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617374573-317813 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 Fri, Apr 02, 2021 at 09:45:12AM +0200, Greg KH wrote: > Why is the buffer alignment considered a "waste" here? If that change > is in Linus's tree and newer kernels (it showed up in 5.4 which was > released quite a while ago), where are the people complaining about it > there? > > I think backporting 59bb47985c1d ("mm, sl[aou]b: guarantee natural > alignment for kmalloc(power-of-two)") seems like the correct thing to do > here to bring things into alignment (pun intended) with newer kernels. It's only a waste for slabs which need things like redzones (eg we could get 7 512-byte allocations out of a 4kB page with a 64 byte redzone and no alignment ; with alignment we can only get four). Since slub can enable/disable redzones on a per-slab basis, and redzones aren't terribly interesting now that we have kasan/kfence, nobody really cares.