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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A4A36C433EF for ; Fri, 25 Mar 2022 09:26:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356963AbiCYJ17 (ORCPT ); Fri, 25 Mar 2022 05:27:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356945AbiCYJ1l (ORCPT ); Fri, 25 Mar 2022 05:27:41 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 78114CF4B3 for ; Fri, 25 Mar 2022 02:26:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648200366; 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=Ct4y/2vagTEoL5DgWAoLz+jJ6PVTSzZLkKcuQNOy3tk=; b=iX/gIIBgBAFJFmYsc7SumuAnIH3k3a1b552wh37n3XyDp0uf+pfx6Tc0TCY5It8QNsU8Yf iHr8ghARlPxUogyf9nEe6Lkmbr3nPRhZE3Umx7do+GyQlzXBeM8ylGKpCiKcYBX4t/ovFH 39ty/CtsB/UTPZgS1h46wGnEp/4WWHc= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-404-2Br8BHt3OfiW6g1sQx0YHQ-1; Fri, 25 Mar 2022 05:26:01 -0400 X-MC-Unique: 2Br8BHt3OfiW6g1sQx0YHQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 976D41044560; Fri, 25 Mar 2022 09:26:00 +0000 (UTC) Received: from ws.net.home (unknown [10.36.112.12]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8A2A12166B2D; Fri, 25 Mar 2022 09:25:55 +0000 (UTC) Date: Fri, 25 Mar 2022 10:25:53 +0100 From: Karel Zak To: Greg KH Cc: Miklos Szeredi , Theodore Ts'o , Christian Brauner , Miklos Szeredi , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Linux API , linux-man , LSM , Ian Kent , David Howells , Linus Torvalds , Al Viro , Christian Brauner , Amir Goldstein , James Bottomley Subject: Re: [RFC PATCH] getvalues(2) prototype Message-ID: <20220325092553.rncxqrjslv6e4c7v@ws.net.home> References: <20220322192712.709170-1-mszeredi@redhat.com> <20220323114215.pfrxy2b6vsvqig6a@wittgenstein> <20220325084646.7g6oto2ce3vou54x@ws.net.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 25, 2022 at 09:54:21AM +0100, Greg KH wrote: > On Fri, Mar 25, 2022 at 09:46:46AM +0100, Karel Zak wrote: > > On Thu, Mar 24, 2022 at 09:44:38AM +0100, Miklos Szeredi wrote: > > > > If so, have you benchmarked lsof using this new interface? > > > > > > Not yet. Looked yesterday at both lsof and procps source code, and > > > both are pretty complex and not easy to plug in a new interface. But > > > I've not yet given up... > > > > I can imagine something like getvalues(2) in lsblk (based on /sys) or > > in lsfd (based on /proc; lsof replacement). The tools have defined set > > of information to read from kernel, so gather all the requests to the > > one syscall for each process or block device makes sense and it will > > dramatically reduce number of open+read+close syscalls. > > And do those open+read+close syscalls actually show up in measurements? > > Again, I tried to find a real-world application that turning those 3 > into 1 would matter, and I couldn't. procps had no decreased system > load that I could notice. I'll mess with lsof but that's really just a > stress-test, not anything that is run all the time, right? Right, the speed of ps(1) or lsof(1) is not important. IMHO the current discussion about getvalues() goes in wrong direction :-) I guess the primary motivation is not to replace open+read+close, but provide to userspace something usable to get information from mount table, because the current /proc/#/mountinfo and notification by poll() is horrible. Don't forget that the previous attempt was fsinfo() from David Howells (unfortunately, it was too complex and rejected by Linus). > And as others have said, using io_uring() would also solve the 3 syscall > issue, but no one seems to want to convert these tools to use that, > which implies that it's not really an issue for anyone :) OK, I'll think about it :-) Karel -- Karel Zak http://karelzak.blogspot.com