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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05145C71153 for ; Mon, 4 Sep 2023 22:10:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240256AbjIDWKb (ORCPT ); Mon, 4 Sep 2023 18:10:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230140AbjIDWKa (ORCPT ); Mon, 4 Sep 2023 18:10:30 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B1959C for ; Mon, 4 Sep 2023 15:10:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=xahJMTjgPcQA+Fj2QnICgP77BNL3/8o+OA1c8sYTjv8=; b=cuItqygV6XF0oYfJ4TFHzRzbfn Svx5rirG2yw/eXov4zG+rNOCmnMK2L/71ekWM8x+wnID3Lq6c4EhHDd0amUwuCxeBeUrQGCUNL0ja 29dji72jaP6LyHfK4m2H77xJqaJIlSxAZDZ+FE65Om1a4Kn+Y7FkUNvNgxV/XR7kCkAj3OlzznfyO Mui63fu6EA2yBQEt4NiDa5G2xui/1LpqMDj78/Sl6TCBjUuEl0VpxKDCCNJrdHoShJXKd1AfsDLOc MF0HlcpCorVkUU7vsRWoH3K/hdYrxbOtr5eT1H9nwAZfy68NMZskRemT1iaK8yoUhJgFC0X5ioeYV phlHDGFw==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qdHll-002qQ5-8w; Mon, 04 Sep 2023 22:10:05 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id E62A8300642; Tue, 5 Sep 2023 00:10:04 +0200 (CEST) Date: Tue, 5 Sep 2023 00:10:04 +0200 From: Peter Zijlstra To: Srikar Dronamraju Cc: Michael Ellerman , linuxppc-dev , Nicholas Piggin , Christophe Leroy , ndesaulniers@google.com, Nathan Lynch , Josh Poimboeuf , Mark Rutland , linux-kernel@vger.kernel.org Subject: Re: [PATCH] powerpc/smp: Dynamically build powerpc topology Message-ID: <20230904221004.GB2568@noisy.programming.kicks-ass.net> References: <20230830122614.73067-1-srikar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230830122614.73067-1-srikar@linux.vnet.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 30, 2023 at 05:56:14PM +0530, Srikar Dronamraju wrote: > Currently there are four powerpc specific sched topologies. These are > all statically defined. However not all these topologies are used by > all powerpc systems. > > To avoid unnecessary degenerations by the scheduler , masks and flags > are compared. However if the sched topologies are build dynamically then > the code is simpler and there are greater chances of avoiding > degenerations. > > Even x86 builds its sched topologies dynamically and new changes are > very similar to the way x86 is building its topologies. You're not stating it explicitly, but you're doing this as a performance optimization, right? The x86 thing didn't particularly care about avoiding degenerate topologies -- it's just that the fixed tables method grew unwieldy due to combinatorics. And how does this patch relate to the other series touching this? powerpc/smp: Shared processor sched optimizations