From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.mainlining.org (mail.mainlining.org [5.75.144.95]) (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 769F7367B7E; Sat, 19 Sep 2026 16:35:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=5.75.144.95 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789835743; cv=none; b=jHODURQsFqnWyMlAt0+w5sjxJ9Li5F4y5eyAE5RXviZE6ANBRgswWd7rDBJSpP9FS6ciRk2UDIY4kpMp3m2MQfScWuoTDfy5uOPCC3x+ffqvPmzJKdseugOv/5uE6H42J+QPWiJCBimVxpKOoMN+zwdoNSitH/wvHjpkoR7lLGg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789835743; c=relaxed/simple; bh=83G8wP1wEtWoW0cUFLtn11NPBN+2XzI+CsyuJfeyx+0=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=Kc7TO5sDuUezAJfpjgb5+kN+XLK6Qgh1tNk/II23IX7htfvA180UMt8c2EsyDayFTOi8xUv0ld4h9SbbishYP8n+ddmvM1vZWZJ7/mLezxeLr7rFCd1aWGNfI9ejzC9/AKlxKCtzpS4F7lZNyiT360XaEDP+mtvTzysmnhsqUBc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org; spf=pass smtp.mailfrom=mainlining.org; dkim=pass (2048-bit key) header.d=mainlining.org header.i=@mainlining.org header.b=RkimT5Bk; dkim=permerror (0-bit key) header.d=mainlining.org header.i=@mainlining.org header.b=6ysdKn0Z; arc=none smtp.client-ip=5.75.144.95 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mainlining.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mainlining.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mainlining.org header.i=@mainlining.org header.b="RkimT5Bk"; dkim=permerror (0-bit key) header.d=mainlining.org header.i=@mainlining.org header.b="6ysdKn0Z" DKIM-Signature: v=1; a=rsa-sha256; s=202507r; d=mainlining.org; c=relaxed/relaxed; h=Message-ID:Subject:To:From:Date; t=1789835686; bh=ss08+m6Ho9dtJTXVBqY3w5Z xBXwOCMfnNt1YuIpmHGs=; b=RkimT5BkBTiAaZt96v8HUbIATDIlAJLAunUMzSNZIDzk9bPrVn GDg6ukzcJtXjd7XQaTG/kpIGy54G06dpI5caJNZpfoyN/OFsc//5rFicIO597d+OG34hfjYJplg fYIsbIc7dPfSJXLQLxzf61IAHFcSebtFnJ2+pKT87v0p0qq8HmRwFs8TLqlGtaeeYB9RQbbbf5v KokwkRsGtkM+qKYYAq2XiVQ24YQvHAgx/SZEY+MnprN8oHGPGwteEueNQ8Aa5HgxCBLhaYIUsbj RzaA9+kTbtkFoxKEkn2sBvZLGaghMwqcDJBAzp1q5R+GuO+bsiQc/lCIqOWm2YBQwtQ==; DKIM-Signature: v=1; a=ed25519-sha256; s=202507e; d=mainlining.org; c=relaxed/relaxed; h=Message-ID:Subject:To:From:Date; t=1789835686; bh=ss08+m6Ho9dtJTXVBqY3w5Z xBXwOCMfnNt1YuIpmHGs=; b=6ysdKn0ZyB1iJMq/zpPI1XK39XVC7xlLiBElhdUCPQ4AVd3HI2 IMLjLff0iUlHgoSDPSjl9nR+oqlFqf9lLfAQ==; Date: Sat, 19 Sep 2026 17:34:47 +0100 From: Bradley Morgan To: Linus Torvalds , "Paul E. McKenney" CC: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Mathieu Desnoyers , Boqun Feng , Steven Rostedt , lkmm@lists.linux.dev, Zqiang , Wang Lian , Kunwu Chan , Nicholas Piggin , Michael Ellerman , Greg Kroah-Hartman , Sebastian Andrzej Siewior , Will Deacon , Peter Zijlstra , Alan Stern , John Stultz , Andrew Morton , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Jonas Oberhauser , linux-mm@kvack.org Subject: Re: [PATCH 01/28] hazptr: Implement Hazard Pointers In-Reply-To: References: <20260919000056.3132131-1-paulmck@kernel.org> Message-ID: <6B1FC39D-6EB0-433A-8E49-E5EFC9379AD7@mainlining.org> 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=utf-8 Content-Transfer-Encoding: 8bit On 19 September 2026 17:30:26 BST, Linus Torvalds wrote: >On Fri, 18 Sept 2026 at 17:01, Paul E. McKenney >wrote: >> >> Its main benefit over RCU is that it allows fast reclaim of >> HP-protected pointers without needing to wait for a grace period. > >So last time I looked at this was some time ago, but the thing I was >missing then seems to still be missing: actual real numbers. > >And no, I most *definitely* do not mean the pointless "do this in a tight >loop". > >That's just garbage. Honestly, when I see those numbers it just makes >me go "I don't want to merge things that even mention this kind of >stupid load". It's worse than irrelevant - it's an actively >misleading. > >So I want to see a real load where this is actually visible not a >"loop a billion times on a hot-cache thing that doesn't do anything". I wanna be a fanboy so bad here but I need to breathe and say something technical I think hazard pointers are good, what test do YOU suggest we do here? Once I get that PowerPC grant I'm happy to run it. God I wanted to be a fanboy and say omg Linus hi, but I'm sure I'll be flamed, sigh. Sigh. > > Linus > --- Thanks! "I'm not a very positive person" - Linus torvalds