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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 3F8EFC43610 for ; Mon, 26 Nov 2018 17:44:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 163292086B for ; Mon, 26 Nov 2018 17:44:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 163292086B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726719AbeK0Eiz (ORCPT ); Mon, 26 Nov 2018 23:38:55 -0500 Received: from outbound-smtp13.blacknight.com ([46.22.139.230]:41674 "EHLO outbound-smtp13.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726255AbeK0Eiz (ORCPT ); Mon, 26 Nov 2018 23:38:55 -0500 Received: from mail.blacknight.com (unknown [81.17.254.26]) by outbound-smtp13.blacknight.com (Postfix) with ESMTPS id 7DFDF1C2E63 for ; Mon, 26 Nov 2018 17:44:04 +0000 (GMT) Received: (qmail 10025 invoked from network); 26 Nov 2018 17:44:04 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[37.228.229.69]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 26 Nov 2018 17:44:04 -0000 Date: Mon, 26 Nov 2018 17:44:02 +0000 From: Mel Gorman To: Johannes Weiner Cc: Tejun Heo , Peter Zijlstra , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: Hackbench pipes regression bisected to PSI Message-ID: <20181126174402.GR23260@techsingularity.net> References: <20181126133420.GN23260@techsingularity.net> <20181126160724.GA21268@cmpxchg.org> <20181126165446.GQ23260@techsingularity.net> <20181126173218.GA22640@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20181126173218.GA22640@cmpxchg.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 26, 2018 at 12:32:18PM -0500, Johannes Weiner wrote: > On Mon, Nov 26, 2018 at 04:54:47PM +0000, Mel Gorman wrote: > > On Mon, Nov 26, 2018 at 11:07:24AM -0500, Johannes Weiner wrote: > > > @@ -509,6 +509,15 @@ config PSI > > > > > > Say N if unsure. > > > > > > +config PSI_DEFAULT_DISABLED > > > + bool "Require boot parameter to enable pressure stall information tracking" > > > + default n > > > + depends on PSI > > > + help > > > + If set, pressure stall information tracking will be disabled > > > + per default but can be enabled through passing psi_enable=1 > > > + on the kernel commandline during boot. > > > + > > > endmenu # "CPU/Task time and stats accounting" > > > > > > > Should this default y on the basis that someone only wants the feature if > > they are aware of it? This is not that important as CONFIG_PSI is disabled > > by default and it's up to distribution maintainers to use their brain. > > I went with the NUMA balancing example again here, which defaults to > enabling the feature at boot time. IMO that makes sense, as somebody > would presumably first read through the PSI help text, then decide y > on that before being asked the second question. A "yes, but > " for vendor kernels seems more appropriate than > requiring a double yes for other users to simply get the feature. > That's fair enough. The original NUMA balancing thinking was that it should be enabled because there is a reasonable expectation that it would improve performance regardless of user awareness. PSI is not necessarily the same as it requires a consumer but I accept that a distro maintainer should read the Kconfig text and figure it out. I'll make sure the updated version gets tested, thanks. -- Mel Gorman SUSE Labs