From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (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 232FB371056; Fri, 12 Jun 2026 08:14:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781252049; cv=none; b=oMt3apQZv8MT0T1uvmpbwutXHCp8++muZqvqMI9PymGkD4O2780uPPECsrOX7ESmHs7/Fh71Tq+rwFIKKjYhbyqacigkfbzGf6pNA3BUOajWOWTCob5rsMOvqNc6N6BVkOzlgiz5xWxdE/GqGHBwof70pgPPpsH4MUjUYsx0V7g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781252049; c=relaxed/simple; bh=MWvRS3F2i64NgpflpEBFFPOcwmTmAqyjCwA4IKLYmH0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=iEjZ4R5nJsCqOaLt6WFFH3NkuVaHjBNYI8q5zkXjY3wQ3n7ezrrRQwBIn9z6/CU6px4cjG/scs4AVj2LD+foAaQu4iYDKlCMFDmOnyiLJRQO4P6F95PJ5SLzv/fBRlJZbqSaEj6Gq/BuWRGO1RqRHAcAypjK/FkjnYjtyFVwmWk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org; spf=pass smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=GTbx/AJ5; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="GTbx/AJ5" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=nzU38H2nZJuLCJBaFR8gZqzBA5+j2zpD5Cb1KHXc6mE=; b=GTbx/AJ5HKW1y1wnI5mWZdyvhr K22mNxauxkh5+qDtL4Mo2vrDXd1Is4IXdlz/FiGGVGyjxLBOIUyLJ/iK7UoN/g4Tu1koWzeE+0JZm NIMQYSacTyoWPCOGNl8ijpq5cfGJGVxgqEjsJcnSnrG8SXVf/RaDDQH3xkiMx1NeBQyqeGtmCgMKn 70mrSGINgk9XOV+/5djfOnfLCMnJpY2IZH3WayOA3/JuHMIXsr2PmYiNQp/vZOl/3b5awB3g5ZRZZ 0oiBpLTM4btAQ2bTwTuixXOiiI1UPRapW6oTf9ggX0b1I43Xvu7D1b86TqpY6PSNlL1XUjZZfntWl l5b5/qpg==; Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1wXx1g-00Ab6d-0t; Fri, 12 Jun 2026 08:14:05 +0000 Date: Fri, 12 Jun 2026 01:13:59 -0700 From: Breno Leitao To: linux-kernel@vger.kernel.org Cc: linux-tip-commits@vger.kernel.org, "Peter Zijlstra (Intel)" , Thomas Gleixner , x86@kernel.org Subject: Re: [tip: locking/core] futex: Optimize futex hash bucket access patterns Message-ID: References: <20260610135510.GB1430057@noisy.programming.kicks-ass.net> <178124827005.1393914.7048476948730678912.tip-bot2@tip-bot2> 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: <178124827005.1393914.7048476948730678912.tip-bot2@tip-bot2> X-Debian-User: leitao On Fri, Jun 12, 2026 at 07:11:10AM +0000, tip-bot2 for Peter Zijlstra wrote: > futex: Optimize futex hash bucket access patterns > > Breno reported significant c2c HITM in a futex hash heavy workload. ... > Funnily this turns out to remove more code than it adds and significantly > improves futex hash performance (as measured by 'perf bench futex hash'): Fascinating! > Reported-by: Breno Leitao > Signed-off-by: Peter Zijlstra (Intel) > Tested-by: Breno Leitao > Tested-by: Thomas Gleixner > Link: https://patch.msgid.link/20260610135510.GB1430057@noisy.programming.kicks-ass.net Thanks so much Peter! --breno