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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 69CE5C43602 for ; Wed, 1 Jul 2026 08:42:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=hIW/bfoVhF6C8YrHlddSaYp+8+PB2sPCZ1uwcJ1svP8=; b=AB4Aeht/z4wXD1rPDNDn/guRGF cNfORTmm5ca+iH88hAfG0BAKh2imCthlHTlkG9mtKVGyIdIVFDbOut9TmGMK8iHrN2RYPsWPQY1Ox LPJp3EVhBWQv/bYdrlKR1WEqaOPzOgQLmfBGa2JmlW6pfly3QL0s0vfnn8g883iv0o6Uf/uXxs/y9 UmycoEG8aSIzZ66FSz0E5NLd6nbL/Q7gM7eNIT4Jdu1pk7lWWHPLs3YUbwV7zIqtxERx2EK+aIsR9 hDLDosJtgpeIhqf7/COY9k/9Qmm9QqOaF+bq2o6ZnlRLM6HOZBQQB68GW9EF1wG5c+EdooepYWIhP ZYRkjApQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1weqW9-000000013FC-2awL; Wed, 01 Jul 2026 08:42:01 +0000 Received: from galois.linutronix.de ([193.142.43.55]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1weqW6-000000013EL-13yh; Wed, 01 Jul 2026 08:41:59 +0000 Date: Wed, 1 Jul 2026 10:41:50 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1782895312; 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:references:references; bh=hIW/bfoVhF6C8YrHlddSaYp+8+PB2sPCZ1uwcJ1svP8=; b=WlkVgNkTFIYNtIj5qhELBYQd+AxKqlkZG3TrLGwri5qEahI5i2Iq5DPX1nRgw4bnbyacTw G6IG8Qy3NuzNrCDMtIbAL5uMpEgdi1pIXIqiIyZJuvq+UJQxYzRGJrpiwLWtT4av1uVvlD RGAbzJcyGPtwci6yrymLNTmaiULCn8ET6Tnkm2/7TuvhZos5optOP0cIInMD0X64zBibOX wlFtEzmKWPN5JwVjZUwN0LY1fw2+Qpa9cS/QY9chuZM14XdjrlPKAF/CfWpGQWzlVWB5Cy hjsnfyncyhqRk3d2cx8c1W7hUUH3sjBIOm/jrY9WePU3JRRm9ynzK2e7bJ681w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1782895312; 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:references:references; bh=hIW/bfoVhF6C8YrHlddSaYp+8+PB2sPCZ1uwcJ1svP8=; b=i5WUD6yceXQe3x8TOrF2eWaGcrFDsh2T9jch8rsli5FTanCRAoIUsTybzMrCtoXwtD6xPq deJ2Wb7rO9Vu+lAg== From: Sebastian Andrzej Siewior To: Peter Zijlstra Cc: K Prateek Nayak , Arnd Bergmann , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Darren Hart , Davidlohr Bueso , =?utf-8?B?QW5kcsOp?= Almeida , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Samuel Holland , Charlie Jenkins , linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, "H. Peter Anvin" , Thomas Huth , Sean Christopherson , Jisheng Zhang , Alexandre Ghiti , Christian Borntraeger , Sven Schnelle Subject: Re: [PATCH v5 8/8] futex: Use runtime constants for __futex_hash() hot path Message-ID: <20260701084150.GNOeboLw@linutronix.de> References: <20260630045531.3939-1-kprateek.nayak@amd.com> <20260630045531.3939-9-kprateek.nayak@amd.com> <20260701075714.GP48970@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260701075714.GP48970@noisy.programming.kicks-ass.net> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260701_014158_435769_EAD9E057 X-CRM114-Status: UNSURE ( 7.96 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2026-07-01 09:57:14 [+0200], Peter Zijlstra wrote: > The big $1M question: does it actually make it go faster? The whole > point here was performance, right? But I'm not seeing numbers showing > how awesome these patches are. I did complain about the about the size of __futex_data which is blown on distro kernels due to CONFIG_NODES_SHIFT=10 on Debian for instance. This makes it go away at no extra price but yeah let me boot a big box and see. If the performance remains unchanged it is still worth considering due to size savings on the average box with 1 node. The biggest box I have access to has four nodes. If I remember correctly, Prateek was saying that AMD has "normal" boxes which would require =9 for normal operation and they do run distro kernels so lowering that value is not an option. Sebastian