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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 AF139C433E0 for ; Wed, 12 Aug 2020 08:29:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E75220774 for ; Wed, 12 Aug 2020 08:29:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VMsxZERn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726507AbgHLI3S (ORCPT ); Wed, 12 Aug 2020 04:29:18 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:34347 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726182AbgHLI3S (ORCPT ); Wed, 12 Aug 2020 04:29:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597220956; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tM7fbBAWWXBkVIey9wZ7wkJQvmojNxlSppUNG5+gS7I=; b=VMsxZERnqmd8x13tXOnHF+vmYVWmCDiZtq/yoGXdkGQVjTdKDjjsnFCEs5rBEr94xcWn0X BhhvcDB0WSSm+82UoSxJsCE2pgQ6a9wDqyWoskwbZlMunWna9BS58AjdXUqNw10r/0dDoa If3Oz8ZF8RCJJHobawfTyzyG8FwJZHk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-99-TlqZyLRKPRmUg1gFsceu9A-1; Wed, 12 Aug 2020 04:29:15 -0400 X-MC-Unique: TlqZyLRKPRmUg1gFsceu9A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5C7551853DB1; Wed, 12 Aug 2020 08:29:13 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-127.rdu2.redhat.com [10.10.120.127]) by smtp.corp.redhat.com (Postfix) with ESMTP id E72998AD14; Wed, 12 Aug 2020 08:29:09 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <1842689.1596468469@warthog.procyon.org.uk> <1845353.1596469795@warthog.procyon.org.uk> <20200811135419.GA1263716@miu.piliscsaba.redhat.com> <52483.1597190733@warthog.procyon.org.uk> To: Miklos Szeredi Cc: dhowells@redhat.com, Linus Torvalds , linux-fsdevel , Al Viro , Karel Zak , Jeff Layton , Miklos Szeredi , Nicolas Dichtel , Christian Brauner , Lennart Poettering , Linux API , Ian Kent , LSM , Linux Kernel Mailing List Subject: Re: file metadata via fs API (was: [GIT PULL] Filesystem Information) MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <98801.1597220949.1@warthog.procyon.org.uk> Date: Wed, 12 Aug 2020 09:29:09 +0100 Message-ID: <98802.1597220949@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Miklos Szeredi wrote: > Worried about performance? Io-uring will allow you to do all those > five syscalls (or many more) with just one I/O submission. io_uring isn't going to help here. We're talking about synchronous reads. AIUI, you're adding a couple more syscalls to the list and running stuff in a side thread to save the effort of going in and out of the kernel five times. But you still have to pay the set up/tear down costs on the fds and do the pathwalks. io_uring doesn't magically make that cost disappear. io_uring also requires resources such as a kernel accessible ring buffer to make it work. You're proposing making everything else more messy just to avoid a dedicated syscall. Could you please set out your reasoning for that? David