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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 94ACEC433DF for ; Sun, 5 Jul 2020 11:47:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 710DB20771 for ; Sun, 5 Jul 2020 11:47:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593949625; bh=iS+dEu4ZlbKVi61KnZ+UXpVxu0dHrpYBvIX4WV8E5m4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=B2zrN0mwkeJLDjCoGTM4TcOgy0RjYdgvUrBjDA9dVHKzQ1bHAxpqcYnaFmcDyce0q MnM3bQgiAuuU139RbUoaRAhADutQMgGZ/IdJlaN5QkKMpLoESwYNcfPqFswGj6IZ8G JYKGJ/jLTwzZHKRsmqFK/bck8eJRM+W2og5YGnxU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726769AbgGELrF (ORCPT ); Sun, 5 Jul 2020 07:47:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:55156 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726454AbgGELrE (ORCPT ); Sun, 5 Jul 2020 07:47:04 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0D71820723; Sun, 5 Jul 2020 11:47:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593949624; bh=iS+dEu4ZlbKVi61KnZ+UXpVxu0dHrpYBvIX4WV8E5m4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1c7gRkP8UaxVu6l1OoEYgLWfENAntRpmlfRdEJxsaxYkWDJ7glW+16ivqzObROx6Y qNzvkQqgD68TqZIIwsevTFQzBaNCHSWlJqgwmjbLYlVcmsjC6idJBNq6O6VI0aK6NG 89qr1JRxgy2i/92FdgY7lUVvt05/uiLfQoMtLbwQ= Date: Sun, 5 Jul 2020 13:47:06 +0200 From: Greg Kroah-Hartman To: Al Viro Cc: mtk.manpages@gmail.com, shuah@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-man@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster Message-ID: <20200705114706.GA1227487@kroah.com> References: <20200704140250.423345-1-gregkh@linuxfoundation.org> <20200704193040.GC2786714@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200704193040.GC2786714@ZenIV.linux.org.uk> Sender: linux-man-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org On Sat, Jul 04, 2020 at 08:30:40PM +0100, Al Viro wrote: > On Sat, Jul 04, 2020 at 04:02:46PM +0200, Greg Kroah-Hartman wrote: > > Here is a tiny new syscall, readfile, that makes it simpler to read > > small/medium sized files all in one shot, no need to do open/read/close. > > This is especially helpful for tools that poke around in procfs or > > sysfs, making a little bit of a less system load than before, especially > > as syscall overheads go up over time due to various CPU bugs being > > addressed. > > Nice series, but you are 3 months late with it... Next AFD, perhaps? Perhaps :) > Seriously, the rationale is bollocks. If the overhead of 2 extra > syscalls is anywhere near the costs of the real work being done by > that thing, we have already lost and the best thing to do is to > throw the system away and start with saner hardware. The real-work the kernel does is almost neglegant compared to the open/close overhead of the syscalls on some platforms today. I'll post benchmarks with the next version of this patch series to hopefully show that. If not, then yeah, this isn't worth it, but it was fun to write. thanks, greg k-h