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,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 18DD4C432C3 for ; Thu, 21 Nov 2019 04:33:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DFE43206CC for ; Thu, 21 Nov 2019 04:33:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726270AbfKUEbu (ORCPT ); Wed, 20 Nov 2019 23:31:50 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:45636 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725819AbfKUEbt (ORCPT ); Wed, 20 Nov 2019 23:31:49 -0500 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iXe7r-00086k-TL; Thu, 21 Nov 2019 04:31:28 +0000 Date: Thu, 21 Nov 2019 04:31:27 +0000 From: Al Viro To: Matthew Wilcox Cc: zhengbin , hughd@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, houtao1@huawei.com, yi.zhang@huawei.com Subject: Re: [PATCH] tmpfs: use ida to get inode number Message-ID: <20191121043127.GA26530@ZenIV.linux.org.uk> References: <1574259798-144561-1-git-send-email-zhengbin13@huawei.com> <20191120154552.GS20752@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191120154552.GS20752@bombadil.infradead.org> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 20, 2019 at 07:45:52AM -0800, Matthew Wilcox wrote: > On Wed, Nov 20, 2019 at 10:23:18PM +0800, zhengbin wrote: > > I have tried to change last_ino type to unsigned long, while this was > > rejected, see details on https://patchwork.kernel.org/patch/11023915. > > Did you end up trying sbitmap? > > What I think is fundamentally wrong with this patch is that you've found a > problem in get_next_ino() and decided to use a different scheme for this > one filesystem, leaving every other filesystem which uses get_next_ino() > facing the same problem. > > That could be acceptable if you explained why tmpfs is fundamentally > different from all the other filesystems that use get_next_ino(), but > you haven't (and I don't think there is such a difference. eg pipes, > autofs and ipc mqueue could all have the same problem. If you think that anyone is willing to pay one hell of a price on each pipe(2)... Note that get_next_ino() is pretty careful about staying within per-cpu stuff most of the time; it hits any cross-CPU traffic only in 1/1024th of calls. This, AFAICS, dirties shared cachelines on each call. And there's a plenty of pipe-heavy workloads, for obvious reasons.