From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 200A118870E for ; Wed, 9 Oct 2024 08:00:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728460858; cv=none; b=bN5c87Utq0udgyIbXFov+9+ZXvB+EiiiQG2VensV2UX8APHq9WpNHTUZrZvENsoJk/zGBd5Q6yAmToFPkiL68muyYG0YDcNz5lhNT7BzacMxa4B4QTpzUmIposnX3dPfE/qtSIdZ77YeVhXwL4Z66FAyBUjDJDbPA9hz7AgIDQE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728460858; c=relaxed/simple; bh=axFQRrF2Y8HkeQ4+fO7T8+Nt4YU1FpmE7EWBJtnvsvg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IEFJLxS8PGxB8nCueGUDERm8IMSHdzhKAqfUgShInRanEwzE+J9zuY5Vwye/D+9kZ9ppz8lCVfN3fWjtdTsZ33rHwOmaM8M6hhPL0qNhbf0WOU9nobNaeShartkLpPhfvSt5WDUH38PhtyVZx3/BvI0Wq0X7pWvHr+AA5cNAHqM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 2FF24227A8E; Wed, 9 Oct 2024 10:00:52 +0200 (CEST) Date: Wed, 9 Oct 2024 10:00:52 +0200 From: Christoph Hellwig To: Tero Kristo Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, axboe@kernel.dk, linux-nvme@lists.infradead.org, sagi@grimberg.me, kbusch@kernel.org Subject: Re: [PATCH 1/1] nvme-pci: Add CPU latency pm-qos handling Message-ID: <20241009080052.GA16711@lst.de> References: <20241004101014.3716006-1-tero.kristo@linux.intel.com> <20241004101014.3716006-2-tero.kristo@linux.intel.com> <20241007061926.GA800@lst.de> <913b063d0638614bc95d92969879d2096ffc0722.camel@linux.intel.com> 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: <913b063d0638614bc95d92969879d2096ffc0722.camel@linux.intel.com> User-Agent: Mutt/1.5.17 (2007-11-01) On Wed, Oct 09, 2024 at 09:45:07AM +0300, Tero Kristo wrote: > Initially, I posted the patch against block layer, but there the > recommendation was to move this closer to the HW; i.e. NVMe driver > level. Even if it is called from NVMe, at lot of the code is not nvme specific. Some of it appears block specific and other pats are entirely generic. But I still don't see how walking cpumasks and updating paramters in far away (in terms of cache lines and pointer dereferences) for every single I/O could work without having a huge performance impact.