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=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 96B19C3F2CE for ; Sun, 1 Mar 2020 09:03:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 707AC214DB for ; Sun, 1 Mar 2020 09:03:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726146AbgCAJCt (ORCPT ); Sun, 1 Mar 2020 04:02:49 -0500 Received: from relay7-d.mail.gandi.net ([217.70.183.200]:52389 "EHLO relay7-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725747AbgCAJCt (ORCPT ); Sun, 1 Mar 2020 04:02:49 -0500 X-Originating-IP: 172.58.43.63 Received: from localhost (unknown [172.58.43.63]) (Authenticated sender: josh@joshtriplett.org) by relay7-d.mail.gandi.net (Postfix) with ESMTPSA id 9D74920006; Sun, 1 Mar 2020 09:02:43 +0000 (UTC) Date: Sun, 1 Mar 2020 01:02:39 -0800 From: Josh Triplett To: Chaitanya Kulkarni Cc: Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg , "linux-kernel@vger.kernel.org" , "linux-nvme@lists.infradead.org" Subject: Re: [PATCH] nvme: Check for readiness more quickly, to speed up boot time Message-ID: <20200301090239.GC216567@localhost> References: <20200229025228.GA203607@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 01, 2020 at 02:01:05AM +0000, Chaitanya Kulkarni wrote: > Nit:- please have a look at the patch subject line and make > sure it is not exceeding the required length. Documentation/process/submitting-patches.rst says "no more than 70-75 characters,", and the summary here is 61. Checkpatch similarly says 75. Is there somewhere I missed that gives a different number? > One question though, have you seen similar kind of performance > improvements when system is booted ? I tested with nvme compiled in, both with one NVMe device and two NVMe devices, and in both cases it provided a *substantial* speedup. I didn't test nvme compiled as a module, but in general I'd expect that if you're trying to optimize initialization time you'd want to build it in. > I took some numbers and couldn't see similar benefit. See [1] :- > > Without :- > > 714.532560-714.456099 = .076461 > 721.189886-721.110845 = .079041 > 727.836938-727.765572 = .071366 > 734.589886-734.519779 = .070107 > 741.244296-741.173503 = .070793 With numbers in this range, I don't see how you could be hitting the 100ms msleep at all, even once, which means this patch shouldn't have any effect on the timing you're measuring. - Josh Triplett