From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752087AbbJSLcN (ORCPT ); Mon, 19 Oct 2015 07:32:13 -0400 Received: from h1446028.stratoserver.net ([85.214.92.142]:35960 "EHLO mail.ahsoftware.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750885AbbJSLcM (ORCPT ); Mon, 19 Oct 2015 07:32:12 -0400 Subject: Re: [PATCH 04/14] init: deps: order network interfaces by link order To: Greg Kroah-Hartman References: <5622956F.80408@ahsoftware.de> <56229B0B.80100@ahsoftware.de> <56229E1A.8010803@ahsoftware.de> <20151017193606.GA2315@kroah.com> <5623272A.1050205@ahsoftware.de> <20151018051443.GA29830@kroah.com> <56232C22.4030502@ahsoftware.de> <20151018055926.GB31909@kroah.com> <56237061.1030006@ahsoftware.de> <5624CCAF.6050404@ahsoftware.de> Cc: Linux Kernel Mailing List , Andrew Morton , Russell King , Grant Likely From: Alexander Holler Message-ID: <5624D4AE.5070203@ahsoftware.de> Date: Mon, 19 Oct 2015 13:31:58 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <5624CCAF.6050404@ahsoftware.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 19.10.2015 um 12:57 schrieb Alexander Holler: > Am 18.10.2015 um 12:11 schrieb Alexander Holler: >> Am 18.10.2015 um 07:59 schrieb Greg Kroah-Hartman: >>> On Sun, Oct 18, 2015 at 07:20:34AM +0200, Alexander Holler wrote: >>>> Am 18.10.2015 um 07:14 schrieb Greg Kroah-Hartman: >>>>> On Sun, Oct 18, 2015 at 06:59:22AM +0200, Alexander Holler wrote: >>>>>> Am 17.10.2015 um 21:36 schrieb Greg Kroah-Hartman: >>>>>> >>>>>>> Again, parallelizing does not solve anything, and causes more >>>>>>> problems >>>>>>> _and_ makes things take longer. Try it, we have done it in the >>>>>>> past and >>>>>>> proven this, it's pretty easy to test :) >>>>>> >>>>>> Just because I'm curious, may I ask how I would test that in the >>>>>> easy way >>>>>> you have in mind? I've just posted the results of my tests (the patch >>>>>> series) but I wonder what you do have in mind. >>>>> >>>>> Use the tool, scripts/bootgraph.pl to create a boot graph of your boot >>>>> sequence. That should show you the drivers, or other areas, that are >>>>> causing your boot to be "slow". >>>> >>>> So I've misunderstood you. I've read your paragraph as that it's >>>> easy to >>>> test parallelizing. >>> >>> Ah, ok, if you want to parallelize everything, add some logic in the >>> driver core where the probe() callback is made to spin that off into a >>> new thread for every call, and when it's done, clean up the thread. >>> That's what I did many years ago to try this all out, if you dig in the >>> lkml archives there's probably a patch somewhere that you can base the >>> work off of to test it yourself. >> >> Hmm, I don't think I will do that because that means to setup a new >> thread for every call. And it doesn't need much imagination (or >> experience) that this introduces quite some overhead. >> >> But maybe it makes sense to try out what I'm doing in my patches, >> starting multiple threads once and then just giving them some work. Will > > After a having second thought on your simple approach to parallelize > stuff, I have to say that it just can't work because just starting a > thread for every probe() totally ignores possible dependencies. > Regardless if using one thread per probe() call or if feeding probe() > calls to just a few threads. > > Maybe that's why previous attempts to parallelize stuff failed. But > that's just an assumption as I'm unaware of these previous attempts. Or to describe it more verbose, if DEBUG is turned on in init/dependencies.c (using my patches), it spits out a summary of groups with initcalls (probe() calls) which are independent from each other and therfore can be called in parallel. E.g. one of my systems this looks so: [ 0.288229] init: vertices: 429 edges 204 count 170 [ 0.288295] init: group 0 length 66 (start 0) [ 0.288329] init: group 1 length 33 (start 66) [ 0.288364] init: group 2 length 13 (start 99) [ 0.288398] init: group 3 length 7 (start 112) [ 0.288432] init: group 4 length 9 (start 119) [ 0.288466] init: group 5 length 8 (start 128) [ 0.288500] init: group 6 length 11 (start 136) [ 0.288534] init: group 7 length 6 (start 147) [ 0.288569] init: group 8 length 4 (start 153) [ 0.288603] init: group 9 length 8 (start 157) [ 0.288637] init: group 10 length 3 (start 165) [ 0.288671] init: group 11 length 2 (start 168) [ 0.288705] init: using 4 threads to call annotated initcalls That means the first group contains 66 initcalls which are called using 4 threads, and, after those have finished, the second group with 33 initcalls will be called in parallel (using the same 4 threads). > Regards, > > Alexander Holler