From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6D059395DA9 for ; Wed, 10 Jun 2026 11:22:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781090558; cv=none; b=UVrPExmKx2GwZk0Pj+WIWOJ7uUeo2CuOeFe5+XPGwGkW/4xHAcQntGCi/0GMsDzhg5mpWD4X+wSV5DNnRseLHYIZTw7HbCkdf0azs2ANnsCWwFYvCXePSBpYYbBq6kSczUKtdYEIIE9G7fmwinJeCmURgi8IgNrrfPgIX+EBUPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781090558; c=relaxed/simple; bh=RTIgn3DX8xxBFCVRCk7lHW0XL+ZJH6OvT7aqyMTuYAY=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=To3N8zUfPBUrum1Addls/ezmdVuM7pieTqqN5QmI3xogfr4RTvDPj6ZoYDIiAkW4AggPgXVm7zcjZNrdZtZxrNqTyecjhc1S5/e4+MwnBW6MKLfKt6wkoJxKb15a3wKqMb3jmAijuJ2WyWekEHb82uzs1upYAsZ4myuN65lzPOA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UwFunhLG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UwFunhLG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68B811F00898; Wed, 10 Jun 2026 11:22:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781090557; bh=bLN84rl98j0DaRvc2T3U/HkXePVi9ZmW8wDe9riXixc=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=UwFunhLGpheGAAlmVNG8TAQ4OJlz2QECZZ/5b00inOL2+9Ld6UF7UKTK9p+Tqx0z1 0/2bBbKlHenA5eI17dYkjCjXZYyLlR5j4rpY3M9Apuw5xuwaKmf3u6sU0rfuzU/lS6 3CKN5IdlYnHAHvHcqLdzz6wRBLexX2eRgxtlyuD1TLUz4VRMPKg7MDKKTyf7VwFDB+ BJu0iBabJoEjgcRpZAc+ovLV1ZqgExnoDa1b6vzSuUq/szAQEUO+o3XiikrneFaW7L 2VS4LqiGXu7RkOsqjiurrkZWyyLkCkM3Ze7sgRIJjEwrT6idOwRjDOYyCSD7b3Jexz USbCSm0xrGQXQ== From: Thomas Gleixner To: Peter Zijlstra , Breno Leitao Cc: Ingo Molnar , Darren Hart , Davidlohr Bueso , =?utf-8?Q?Andr=C3=A9?= Almeida , linux-kernel@vger.kernel.org, puranjay@kernel.org, rmikey@meta.com, stuclar@meta.com, namhyung@kernel.org, kernel-team@meta.com Subject: Re: [PATCH RFC] futex: avoid false sharing between hb->chain and the bucket lock In-Reply-To: <20260609201809.GA1430057@noisy.programming.kicks-ass.net> References: <20260605-futex-v1-1-4ad4a0d6f265@debian.org> <20260609104603.GA48970@noisy.programming.kicks-ass.net> <20260609201117.GA187714@noisy.programming.kicks-ass.net> <20260609201809.GA1430057@noisy.programming.kicks-ass.net> Date: Wed, 10 Jun 2026 13:22:34 +0200 Message-ID: <87h5na3ait.ffs@fw13> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Tue, Jun 09 2026 at 22:18, Peter Zijlstra wrote: > On Tue, Jun 09, 2026 at 10:11:17PM +0200, Peter Zijlstra wrote: >> Anyway, how does something like the below work for you? It's a total >> hack job, but it (sorta) builds and runs. >> > > Please use this one, I spotted a silly bug. So I ran this on two machines. SKL dual socket 112 threads: Baseline Patched shared (16k) 1571857 1641435 + 4.4% autosize (512) 646390 903371 +39.7% -b 256 464395 587014 +26.4% -b 512 715687 995943 +39.2% -b 1024 995085 1396328 +40.3% -b 2048 1293114 1668395 +29.0% -b 4096 2124438 2240228 + 5.5% Zen3 dual socket 256 threads: Baseline Patched shared (16k) 1275840 1381279 + 8.2% autosize (512) 1252745 1482179 +18.3% -b 256 856274 955455 +11.5% -b 512 1267490 1544010 +21.8% -b 1024 1424013 1625424 +14.1% -b 2048 1505181 1669342 +10.9% -b 4096 1465993 1688932 +15.2%