From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 DE3E63BFAFB for ; Wed, 10 Jun 2026 11:25:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781090762; cv=none; b=GnMxCUOFPOsOQNzL3ywBa5F4kigkF84OU8b6zmbFzAIwv/fIYoI+QdGMDMW6VMNsAW7VDCKLfdpXP+ZZcB/x5VSErp90BxXQL72JjXHH6T/8nwIfoIyqn0fx6z8HWX97wOvxsfLtsixRtlvsNByWiYnF+Uv1ZsdgD1Wf/rXUKU4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781090762; c=relaxed/simple; bh=5BZCo1Jx5AfKuGj1IVGhi0P6bvFo1vv6QqoDJAzDfWw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i9GhPMtuKI8U+JuOxVPS/7qIBKJzJ3ENqdfVTWiWhmlMeZHY7S4MPaKdIajD/7DeXv+DOvOY1Rpw7eILj32F1JOzgmFzt6N5gBjnvVGSm/w0DWsbYCfDa+7LwCvr7C9A2FIc8z0CJFrlN4oaaW6nVS6sL3x/MIwIxRrNzWioXRo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=tlGH/4/Z; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="tlGH/4/Z" 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=SQmna6E1kiiRsN4xg2DW9gOUaQnFnFefhJyeGpbf4zQ=; b=tlGH/4/Zc0alp5j6ge5ZSuBURU X8rzCKKQhNnWj7lZXux2PTVzEAXLtXmbG/+kSntlMCms2aAvKcL9GmYe2nJKjyD6fKI7aVh8Tf9Qk v90hG/GWe5dMsnGwr3/9RD1FzU68CFmhcZcEd4j0u9mJ5UhICvt3sIH+o4RTHVZbcYCAnXl/Z7gGD rGZOJbgjZqi0BpgBTvhQigqCz/H6iobqYOQ7NAA6/2sU/kugse7Hq1Erl8s64P+MDTfJ/DNlLtQu2 69BIqU2np+qb0MChcgZKugA1U2onkFIC8bL9CzoNRVhcdn6Ei5vpZv4QjZmglwt6zPUP2lcau4k/+ /eq0Jojg==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wXH47-0000000HU3v-2MVn; Wed, 10 Jun 2026 11:25:48 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C351C30036F; Wed, 10 Jun 2026 13:25:46 +0200 (CEST) Date: Wed, 10 Jun 2026 13:25:46 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: Breno Leitao , Ingo Molnar , Darren Hart , Davidlohr Bueso , =?iso-8859-1?Q?Andr=E9?= 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 Message-ID: <20260610112546.GE187714@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> <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; charset=us-ascii Content-Disposition: inline In-Reply-To: <87h5na3ait.ffs@fw13> On Wed, Jun 10, 2026 at 01:22:34PM +0200, Thomas Gleixner wrote: > 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% I suppose that means I'd better go make it prettier and survive randconfig :-)