From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S939071AbdEYTCE (ORCPT ); Thu, 25 May 2017 15:02:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:42900 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760437AbdEYTCA (ORCPT ); Thu, 25 May 2017 15:02:00 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1141C23A0D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mcgrof@kernel.org MIME-Version: 1.0 In-Reply-To: <20170525182655.GD29859@dtor-ws> References: <20170519215829.GE19281@dtor-ws> <20170525162201.GV8951@wotan.suse.de> <20170525163857.GC26128@dtor-ws> <20170525173002.GC29859@dtor-ws> <20170525180603.GZ8951@wotan.suse.de> <20170525182655.GD29859@dtor-ws> From: "Luis R. Rodriguez" Date: Thu, 25 May 2017 12:01:37 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count To: Dmitry Torokhov Cc: Tom Gundersen , Filipe Manana , "Paul E. McKenney" , "linux-doc@vger.kernel.org" , rgoldwyn@suse.com, hare , Jonathan Corbet , Linus Torvalds , linux-kselftest@vger.kernel.org, Andrew Morton , Dan Williams , Aaron Tomlin , rwright@hpe.com, Heinrich Schuchardt , Michal Marek , martin.wilck@suse.com, Rusty Russell , Jeff Mahoney , Ingo Molnar , Petr Mladek , Guenter Roeck , "Eric W. Biederman" , shuah@kernel.org, DSterba@suse.com, Kees Cook , Greg Kroah-Hartman , Josh Poimboeuf , Arnaldo Carvalho de Melo , Miroslav Benes , NeilBrown , "linux-kernel@vger.kernel.org" , David Miller , Jessica Yu , Subash Abhinov Kasiviswanathan Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 25, 2017 at 11:26 AM, Dmitry Torokhov wrote: > On Thu, May 25, 2017 at 08:06:03PM +0200, Luis R. Rodriguez wrote: >> On Thu, May 25, 2017 at 10:38:40AM -0700, Luis R. Rodriguez wrote: >> > On Thu, May 25, 2017 at 10:30 AM, Dmitry Torokhov >> > > There is >> > > no slippery slope for systems to move away, no need to backport >> > > anything. We seem to agree that a better solution is possible (throttle >> > > number of concurrently running modprobes without killing requesters), >> > > and with that solution the band-aid will no longer be needed. >> > > >> > > So please implement and post the proper fix for the issue. >> > >> > Alright, will do away with this patch and just go for the jugular of the issue. >> >> I gave this some more thought, even if we go with the throttling right away in >> practice you'll end up with a dmesg notice of a throttle kicking in once you *do* > > So remove it. The warning was meaningful when we rejected requests, now > it is not. Great. >> reach this. We are forcing only 50 concurrent threads and making this a static >> limit with no good reason than 2.3.38 days evaluation from 16 years ago (2000). >> If we throttle we are going to throttle with a 2.3.38 days limit. And you >> advocate that ? > > Yes. Can you give me reason why slamming the system with more than 50 > modprobes is a good idea in 4.12 days? Does the increased limit > decreases boot time? By how much? If in practice we are not hitting the limit the point is moot, and when we do I agree we can re-evaluate. With my stress test driver on a test case we can push as hard as bringing out the OOM killer even if we throttle, fun. Luis