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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 38A6EC432C0 for ; Mon, 18 Nov 2019 11:58:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18FAB2068D for ; Mon, 18 Nov 2019 11:58:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726654AbfKRL6g (ORCPT ); Mon, 18 Nov 2019 06:58:36 -0500 Received: from mx2.suse.de ([195.135.220.15]:36096 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726506AbfKRL6g (ORCPT ); Mon, 18 Nov 2019 06:58:36 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 8773EABBD; Mon, 18 Nov 2019 11:58:34 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 1E31B1E422A; Mon, 18 Nov 2019 10:35:44 +0100 (CET) Date: Mon, 18 Nov 2019 10:35:44 +0100 From: Jan Kara To: "Theodore Y. Ts'o" Cc: Jan Kara , Sebastian Siewior , Thomas Gleixner , Matthew Wilcox , LKML , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Anna-Maria Gleixner , Steven Rostedt , Julia Cartwright , Alexander Viro , Jan Kara , Mark Fasheh , Joseph Qi , Christoph Hellwig , Joel Becker Subject: Re: [PATCH] fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular spinlock_t Message-ID: <20191118093544.GA17319@quack2.suse.cz> References: <20190820170818.oldsdoumzashhcgh@linutronix.de> <20190820171721.GA4949@bombadil.infradead.org> <20191011112525.7dksg6ixb5c3hxn5@linutronix.de> <20191115145638.GA5461@quack2.suse.cz> <20191115173634.GC23689@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191115173634.GC23689@mit.edu> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri 15-11-19 12:36:34, Theodore Y. Ts'o wrote: > On Fri, Nov 15, 2019 at 03:56:38PM +0100, Jan Kara wrote: > > With some effort, we could even shrink struct buffer_head from 104 bytes > > (on x86_64) to 96 bytes but I don't think that effort is worth it (I'd find > > it better use of time to actually work on getting rid of buffer heads > > completely). > > Is that really realistic? All aside from the very large number of > file systems which use buffer_heads that would have to be reworked, > the concept of buffer heads is pretty fundamental to how jbd2 is > architected. I think it is reasonably possible to remove buffer_heads from data path (including direct IO path) of all filesystems. That way memory consumption of buffer_heads becomes mostly irrelevant and we can have a look how much from the current bh framework still makes sense... Honza -- Jan Kara SUSE Labs, CR