Re: [PATCH v6 01/13] mm/demotion: Add support for explicit memory tiers

From: Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
To: Johannes Weiner <hannes@cmpxchg.org>, Ying Huang <ying.huang@intel.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
	Wei Xu <weixugc@google.com>, Greg Thelen <gthelen@google.com>,
	Yang Shi <shy828301@gmail.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Tim C Chen <tim.c.chen@intel.com>,
	Brice Goglin <brice.goglin@gmail.com>,
	Michal Hocko <mhocko@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Hesham Almatary <hesham.almatary@huawei.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Alistair Popple <apopple@nvidia.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Feng Tang <feng.tang@intel.com>,
	Jagdish Gediya <jvgediya@linux.ibm.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v6 01/13] mm/demotion: Add support for explicit memory tiers
Date: Mon, 13 Jun 2022 18:58:43 +0530	[thread overview]
Message-ID: <080d64c3-1289-49c4-f4a0-105e5266a6f0@linux.ibm.com> (raw)
In-Reply-To: <Yqc4nSEuso+YmPE7@cmpxchg.org>

On 6/13/22 6:46 PM, Johannes Weiner wrote:
> On Mon, Jun 13, 2022 at 01:30:08PM +0800, Ying Huang wrote:
>> On Mon, 2022-06-13 at 09:01 +0530, Aneesh Kumar K V wrote:
>>> On 6/13/22 8:52 AM, Ying Huang wrote:
>>>> On Fri, 2022-06-10 at 19:22 +0530, Aneesh Kumar K.V wrote:
>>>>> +config TIERED_MEMORY
>>>>> +	def_bool NUMA
>>>>> +
>>>>
>>>> As Yang pointed out, why not just use CONFIG_NUMA?  I suspect the
>>>> added value of CONIFIG_TIRED_MEMORY.
>>>
>>> I decided to use TIERED_MEMORY to bring more clarity. It should be same
>>> now that we have moved CONFIG_MIGRATION dependencies to runtime. IMHO
>>> having CONFIG_TIERED_MEMORY is better than using CONFIG_NUMA.
>>
>> I don't think CONFIG_TIERED_MEMORY bring no much value.  It's better
>> to use CONFIG_NUMA directly.  But this is just my opinion.
> 
> I agree. As long as it's always built with CONFIG_NUMA, it's simply
> NUMA code. Easy enough to modularize it later if somebody really wants
> this to be configurable separately.

I was comparing,

#ifdef CONFIG_TIERED_MEMORY
struct memory_tier {

vs

#ifdef CONFIG_NUMA
struct memory_tier {

I will switch to CONFIG_NUMA in the next update since you are not 
finding it beneficial.

-aneesh