Re: [RFC PATCH 0/3] Cgroup accounting of memory tier usage

From: Ying Huang <ying.huang@intel.com>
To: Tim Chen <tim.c.chen@linux.intel.com>,
	linux-mm@kvack.org, akpm@linux-foundation.org
Cc: Wei Xu <weixugc@google.com>, Greg Thelen <gthelen@google.com>,
	Yang Shi <shy828301@gmail.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	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>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
	Shakeel Butt <shakeelb@google.com>
Subject: Re: [RFC PATCH 0/3] Cgroup accounting of memory tier usage
Date: Wed, 15 Jun 2022 12:58:50 +0800	[thread overview]
Message-ID: <68b6a7e92d48a3285a5707378459bb9ae805f333.camel@intel.com> (raw)
In-Reply-To: <cover.1655242024.git.tim.c.chen@linux.intel.com>

On Tue, 2022-06-14 at 15:25 -0700, Tim Chen wrote:
> For controlling usage of a top tiered memory by a cgroup, accounting
> of top tier memory usage is needed.  This patch set implements the
> following:
> 
> Patch 1 introduces interface and simple implementation to retrieve
> 	cgroup tiered memory usage
> Patch 2 introduces more efficient accounting with top tier memory page counter 
> Patch 3 provides a sysfs interface to repot the the top tiered memory
> 	usage.
> 
> The patchset works with Aneesh's v6 memory-tiering implementation [1].
> It is a preparatory patch set before introducing features to
> control top tiered memory in cgroups.
> 
> I'll like to first get feedback to see if 
> (1) Controllng the topmost tiered memory is enough 
> or
> (2) Multiple tiers at the top levels need to be grouped into "toptier"
> or

If we combine top-N tiers, I think the better name could be "fast-tier",
in contrast to "slow-tier".

> (3) There are use cases not covered by (1) and (2). 

Is it necessary to control memory usage of each tier (except the
lowest/slowest)?  I am not the right person to answer the question, but
I want to ask it.

Best Regards,
Huang, Ying

> Thanks.
> 
> Tim
> 
> [1] https://lore.kernel.org/linux-mm/20220610135229.182859-1-aneesh.kumar@linux.ibm.com/ 
> 
> Tim Chen (3):
>   mm/memory-tiers Add functions for tier memory usage in a cgroup
>   mm/memory-tiers: Use page counter to track toptier memory usage
>   mm/memory-tiers: Show toptier memory usage for cgroup
> 
>  include/linux/memcontrol.h   |  1 +
>  include/linux/memory-tiers.h |  2 +
>  mm/memcontrol.c              | 86 +++++++++++++++++++++++++++++++++++-
>  mm/memory-tiers.c            |  3 +-
>  4 files changed, 89 insertions(+), 3 deletions(-)
> 