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 A37BE321F4C for ; Wed, 10 Sep 2025 15:39:31 +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=1757518773; cv=none; b=jERRh9//D26hxIrDNOLUfG+vOCiJbbMwEs9JzDRP2fjQyMBMEf9C7d0jL8mvuz1GSWLtsDcSPX98wiEEf6Ad1y4UB3d1wCXumxJiY3K521DbBKuiPMGbe4w3NuVFURxhf8UDq3QUPyTvovAFmLG0zw3KcVq+5zH7w5dP/DaDuV8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757518773; c=relaxed/simple; bh=ScGfjgTqFriy4iKUBi4MfpAdnEin1NzVLHFkLtuzPEk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mZGB/alTMdGXb1sTrtE2+G7apRxjkC61zFTbZ3o61p0onQtQzOn7mJ19PLRncehMUKN8bMZxfb+m46ri2RslYqDvdeabDS1vJxT0Mh2mHghOlM+YLM5lTfwlqBJiJOZU3PHhb2fhk9DjMbUJdBiM1bsRxH8V1D2R5edRHClQIg8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=kzR6a25V; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none 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="kzR6a25V" 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=CUutveEyfKqm5cx/LfUOapSR3j4/ulAO8at0Pp1NTFE=; b=kzR6a25VrUvMlMmbSCZhp+Czc6 Sak7r1ylr5JNvroWqy7LTUK8Gz4Xaw4CyeFBQsOpShvsb4P0kjH2FW4KxqyUfGPl6BLsL2lAzfL1Q OzyoFj9V/erJWmxACdvpYck0kfmymzPEJa72mnSJDxrUCJ7Bbfz59NA0qaptSDfCS6Yr67CRdByxF EUeCMdMmTx3dMwpsPGXVBiKLVM1PwTga2ZazfaS7vi4p+AQ5hCxT+xKv5MZ8o6pEYOOJ/eALxvSTc 1DEjj5nw1CdGpy9U9SmKkQgS6oEpYh5L4PhWXQKirs3U0GtL+uea7X1+aY6ynLAaVVPf30+JvV37t GT7DQ4Wg==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwMui-0000000BFcE-3PjP; Wed, 10 Sep 2025 15:39:16 +0000 Date: Wed, 10 Sep 2025 16:39:16 +0100 From: Matthew Wilcox To: Bharata B Rao Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jonathan.Cameron@huawei.com, dave.hansen@intel.com, gourry@gourry.net, hannes@cmpxchg.org, mgorman@techsingularity.net, mingo@redhat.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, sj@kernel.org, weixugc@google.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, nifan.cxl@gmail.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, akpm@linux-foundation.org, david@redhat.com, byungchul@sk.com, kinseyho@google.com, joshua.hahnjy@gmail.com, yuanchu@google.com, balbirs@nvidia.com, alok.rathore@samsung.com Subject: Re: [RFC PATCH v2 0/8] mm: Hot page tracking and promotion infrastructure Message-ID: References: <20250910144653.212066-1-bharata@amd.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: <20250910144653.212066-1-bharata@amd.com> On Wed, Sep 10, 2025 at 08:16:45PM +0530, Bharata B Rao wrote: > This patchset introduces a new subsystem for hot page tracking > and promotion (pghot) that consolidates memory access information > from various sources and enables centralized promotion of hot > pages across memory tiers. Just to be clear, I continue to believe this is a terrible idea and we should not do this. If systems will be built with CXL (and given the horrendous performance, I cannot see why they would be), the kernel should not be migrating memory around like this.