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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 2859BC433DB for ; Thu, 25 Feb 2021 11:45:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CBB0564F10 for ; Thu, 25 Feb 2021 11:45:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231771AbhBYLp1 (ORCPT ); Thu, 25 Feb 2021 06:45:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:59660 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231414AbhBYLp0 (ORCPT ); Thu, 25 Feb 2021 06:45:26 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8B84764F17; Thu, 25 Feb 2021 11:44:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614253486; bh=xy4njwEXwUHtCcofc5JLTqOxp8GdsOi4wj5TWjxjKKA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=F8rxJ2I19KhVJGHdH8FpTcgTrLzwoX8Zj3CKwSTeurQ/0OQ6s9Y1W/MuuE4Y4Z05u ugP/QuTV5ft4GxLvP8rkR9QVAGVeyaBPGWnebcLCHbir6hpmGLLSPa7UOKo6mvNs5g JPiKEq2MZ1CDI8T5xjogXlhZfr0RyHdAkHQ3eMys= Date: Thu, 25 Feb 2021 12:44:43 +0100 From: Greg KH To: Yogesh Lal Cc: rafael@kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, pkondeti@codeaurora.org, neeraju@codeaurora.org Subject: Re: [PATCH] driver core: Use unbound workqueue for deferred probes Message-ID: References: <1614167749-22005-1-git-send-email-ylal@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Thu, Feb 25, 2021 at 04:03:50PM +0530, Yogesh Lal wrote: > Hi Greg, > > > On 2/24/2021 6:13 PM, Greg KH wrote: > > On Wed, Feb 24, 2021 at 05:25:49PM +0530, Yogesh Lal wrote: > > > Queue deferred driver probes on unbounded workqueue, to allow > > > scheduler better manage scheduling of long running probes. > > > > Really? What does this change and help? What is the visable affect of > > this patch? What problem does it solve? > > > > We observed boot up improvement (~400 msec) when the deferred probe work is > made unbound. This is due to scheduler moving the worker running deferred > probe work to big CPUs. without this change, we see the worker is running on > LITTLE CPU due to affinity. Why is none of this information in the changelog text? How are we supposed to know this? And is this 400msec out of 10 seconds or something else? Also, this sounds like your "little" cpus are really bad, you might want to look into fixing them first :) But if you really want to make this go faster, do not deferr your probe! Why not fix that problem in your drivers instead? > Please let us now if there are any concerns/restrictions that deferred probe > work should run only on pinned kworkers. Since this work runs deferred probe > of several devices , the locality may not be that important Can you prove that it is not important? I know lots of gyrations are done in some busses to keep probe happening on the same CPU for very good reasons. Changing that should not be done lightly as you will break this. thanks, greg k-h