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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 52723C433B4 for ; Thu, 13 May 2021 00:23:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2DE2D613CA for ; Thu, 13 May 2021 00:23:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235656AbhEMAYE (ORCPT ); Wed, 12 May 2021 20:24:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346258AbhEMAWW (ORCPT ); Wed, 12 May 2021 20:22:22 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1018EC061359 for ; Wed, 12 May 2021 16:58:18 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1620863896; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to; bh=CX9+MuuWEQWnFC1f0v4umjM+QedIzoRjhbbbY3SBY/Y=; b=ZNDkANDGwRROjrzWGWRElNOkfA4C5+41NwZ2A9s0gdQwx+QiRLzwLdaNUx8Wf3ThiIpe+b n+1R3bNi0O0QftDuxj2Fw6T1I0LntXzBhPb667WmYCLm+Lpodyx1cHkc1pQvoZbmzLHrbm ecG+QYYA/4kdnMHBa8BSYfi/2oAu7plqeh81l1/JlUehY5fUVrT4o4AAVHWQDXet5Imc74 kcDJKfxytEAI4yeEjnK2pA4n64S8S//KKe8G5BfgMcvoF6ufO9FTzqHUm71eHR+HCxNW8a cH1FG/qpR3x4qv77ndbn/EUlLb0BWUWW2g0T3EoTBggEaqOt50j7EbheX3KCWw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1620863896; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to; bh=CX9+MuuWEQWnFC1f0v4umjM+QedIzoRjhbbbY3SBY/Y=; b=o7kCPiWS7RzQ4S/OEGRUHYOByNw8Pm0MPlWue0VP2qZAaMZENXhqfU2lI/HUAOhahAEaS/ oe6Jw92bhcThLABQ== To: Alexey Dobriyan , mingo@redhat.com, peterz@infradead.org Cc: linux-kernel@vger.kernel.org, Alexey Dobriyan , x86@kernel.org Subject: Re: [PATCH 1/4] sched: make nr_running() return 32-bit In-Reply-To: <20210422200228.1423391-1-adobriyan@gmail.com> Date: Thu, 13 May 2021 01:58:16 +0200 Message-ID: <87fsyr5wtj.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alexey, On Thu, Apr 22 2021 at 23:02, Alexey Dobriyan wrote: > Creating 2**32 tasks is impossible due to futex pid limits and wasteful > anyway. Nobody has done it. > this whole pile lacks useful numbers. What's the actual benefit of that churn? Just with the default config for one of my reference machines: text data bss dec hex filename 16679864 6627950 1671296 24979110 17d26a6 ../build/vmlinux-before 16679894 6627950 1671296 24979140 17d26c4 ../build/vmlinux-after ------------------------------------------------------------------------ +30 I'm truly impressed by the massive savings of this change and I'm even more impressed by the justification: > Bring nr_running() into 32-bit world to save on REX prefixes. Aside of the obvious useless churn, REX prefixes are universaly true for all architectures, right? There is a world outside x86 ... Thanks, tglx