From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 9D46E206F17 for ; Tue, 4 Feb 2025 09:28:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738661296; cv=none; b=qFrZyORUsss+j3D2XcTtDkPHYWPE6XW5ajw9tSeQFP6d1wujbU974gXfQ6cujgkxFV0t9w2umicedLcihT/aD08//NLBvpVKRF7D2LXVYlKBhZsshzyEIgsscbJDQFrZOKH4pvzYIZgyh0gxgYqu1rtz2tcJFSVX61l9Akm8X28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738661296; c=relaxed/simple; bh=65JVhxdXQGsMohzOnNWRBzY67jDzX0XfRFA5pfUh9no=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=R8NQQnKKs809oGPFmMJmZj/URCF41MqdIWVO3AHLjwYv8gziWSAGhd5gJYK5ZTDeADLoXQgFBtbZU54WMzHXwHKOFyc/a0MwPpgMLbzZ+XwEzQ1ZDiJwN81lYEkr40wMWNl8Q98cL9TFaRwVZVYRh9mddb2ufCyj5clPi7srkfE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=mCGhPS0D; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=A1r3nAQJ; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="mCGhPS0D"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="A1r3nAQJ" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1738661292; 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=IxUhzMpZbBLI24vAgo0RXEQvd0b3kP29hyIxwVLwatQ=; b=mCGhPS0DHUwuRWQm44gBhIszb1e72y/U7MORY7e66FXUq8YfBscCibIJBeEuKpwLftqM8l G+OkrEUa7O4vwTxbVRfpXNlMgEKmrc79ZU0m/vlE+y5DPAFaNcv8rk0nF5yO2RaYPT/Z2t JoQ8MkcwIJyuG1SemB8Yxc3x+5HJlBylEvoCzTIc+q8IRnc2LA2/eXJtZRg+5ptfqUyP9F RDMNarbt+REFMqA/GlLMwTHLF893O3yDYRGVXSvErl00k3BqmV8EowThZTH46F3dIR5m6d Fkcv9rDEoey8/f3oerIy6TyoiNt8EgQjQJwlK0mzxvQEMh/m/VHnzL/JcpN65g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1738661292; 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=IxUhzMpZbBLI24vAgo0RXEQvd0b3kP29hyIxwVLwatQ=; b=A1r3nAQJfG/G6wJiuEXiKyr4CHoP6qmmv5LtlQPq/j+V1yTRs7ebuXhDYIcbs90Nf2BW+Y F5Ik50dM03CFevDA== To: Peter Zijlstra , Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, =?utf-8?Q?Andr=C3=A9?= Almeida , Darren Hart , Davidlohr Bueso , Ingo Molnar , Juri Lelli , Valentin Schneider , Waiman Long Subject: Re: [PATCH v8 03/15] futex: Add basic infrastructure for local task local hash. In-Reply-To: <20250204084135.GN7145@noisy.programming.kicks-ass.net> References: <20250203135935.440018-1-bigeasy@linutronix.de> <20250203135935.440018-4-bigeasy@linutronix.de> <20250203144101.GL7145@noisy.programming.kicks-ass.net> <20250203155251.cAKJlgIZ@linutronix.de> <20250204084135.GN7145@noisy.programming.kicks-ass.net> Date: Tue, 04 Feb 2025 10:28:11 +0100 Message-ID: <87ldumnjo4.ffs@tglx> 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, Feb 04 2025 at 09:41, Peter Zijlstra wrote: > On Mon, Feb 03, 2025 at 04:52:51PM +0100, Sebastian Andrzej Siewior wrote: >> On 2025-02-03 15:41:01 [+0100], Peter Zijlstra wrote: >> > Notably, I'm also still thikning about all that pending FUTEX2_NUMA >> > stuff. >> >> With local-hash there is still room for FUTEX2_NUMA? > > Yes, single process can span multiple nodes, and then you still get the > cross node contention issues. This is strictly about process private futexes, while FUTEX2_NUMA covers both shared and private futexes and helps to avoid the hash collision and resulting contention problems which are caused by the current global hash. With the private futex seperation you obviously get the cross node memory access problems, but not the general contention issues which FUTEX2_NUMA tries to address. Thanks, tglx