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 84361C3F2D1 for ; Wed, 4 Mar 2020 16:49:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5BEF824654 for ; Wed, 4 Mar 2020 16:49:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583340564; bh=htZq3MKYG3/FJ8bILu0qqA54TuTZg4n2O0B4bA60sUA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=zlEIfAgyddNQO1SKfbYToPzidK5cCjHOSF5lb9XD4X/MVdZoaanLc2xsQYt/c8tSQ mmO29xTNr7g+NT0Sb7XyU6Vn2HA1VXW5bvCajTldQOYMAwB/Ets7YD68VJhpksjKzj 4PiV0o+8nqagoq1ipJMiY1rveqJTMUbZqDl52PAA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388260AbgCDQtV (ORCPT ); Wed, 4 Mar 2020 11:49:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:35754 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388063AbgCDQtV (ORCPT ); Wed, 4 Mar 2020 11:49:21 -0500 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 D2C2922B48; Wed, 4 Mar 2020 16:49:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583340556; bh=htZq3MKYG3/FJ8bILu0qqA54TuTZg4n2O0B4bA60sUA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QFw/Q1NY4B+y7WTrekje+ZpgNyFzrIcZ7UTABnDsnjgXf0am4nQsbW5ZVxTNNjWld 6g3+cMHNGJFGxmjYQ7wuvpNbSuU4C8wJW0QIQn6siOMOjhXevPQyX+4tWUsOTV/oDy NWsKv9WocDxBZSqHQrN8bsD7sTiXcsBN4pte4wXQ= Date: Wed, 4 Mar 2020 17:49:13 +0100 From: Greg Kroah-Hartman To: Karel Zak Cc: Ian Kent , Miklos Szeredi , David Howells , Christian Brauner , James Bottomley , Steven Whitehouse , Miklos Szeredi , viro , Christian Brauner , Jann Horn , "Darrick J. Wong" , Linux API , linux-fsdevel , lkml Subject: Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17] Message-ID: <20200304164913.GB1763256@kroah.com> References: <107666.1582907766@warthog.procyon.org.uk> <0403cda7345e34c800eec8e2870a1917a8c07e5c.camel@themaw.net> <1509948.1583226773@warthog.procyon.org.uk> <20200303113814.rsqhljkch6tgorpu@ws.net.home> <20200303130347.GA2302029@kroah.com> <33d900c8061c40f70ba2b9d1855fd6bd1c2b68bb.camel@themaw.net> <20200304152241.iaiulvl5xisnuxp6@ws.net.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200304152241.iaiulvl5xisnuxp6@ws.net.home> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Mar 04, 2020 at 04:22:41PM +0100, Karel Zak wrote: > On Wed, Mar 04, 2020 at 10:01:33AM +0800, Ian Kent wrote: > > On Tue, 2020-03-03 at 14:03 +0100, Greg Kroah-Hartman wrote: > > > Actually, I like this idea (the syscall, not just the unlimited > > > beers). > > > Maybe this could make a lot of sense, I'll write some actual tests > > > for > > > it now that syscalls are getting "heavy" again due to CPU vendors > > > finally paying the price for their madness... > > > > The problem isn't with open->read->close but with the mount info. > > changing between reads (ie. seq file read takes and drops the > > needed lock between reads at least once). > > readfile() is not reaction to mountinfo. > > The motivation is that we have many places with trivial > open->read->close for very small text files due to /sys and /proc. The > current way how kernel delivers these small strings to userspace seems > pretty inefficient if we can do the same by one syscall. > > Karel > > $ strace -e openat,read,close -c ps aux > ... > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 43.32 0.004190 4 987 read > 31.42 0.003039 3 844 4 openat > 25.26 0.002443 2 842 close > ------ ----------- ----------- --------- --------- ---------------- > 100.00 0.009672 2673 4 total > > $ strace -e openat,read,close -c lsns > ... > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 39.95 0.001567 2 593 openat > 30.93 0.001213 2 597 close > 29.12 0.001142 3 365 read > ------ ----------- ----------- --------- --------- ---------------- > 100.00 0.003922 1555 total > > > $ strace -e openat,read,close -c lscpu > ... > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 44.67 0.001480 7 189 52 openat > 34.77 0.001152 6 180 read > 20.56 0.000681 4 140 close > ------ ----------- ----------- --------- --------- ---------------- > 100.00 0.003313 509 52 total As a "real-world" test, would you recommend me converting one of the above tools to my implementation of readfile to see how/if it actually makes sense, or do you have some other tool you would rather see me try? thanks, greg k-h