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Message-ID: <13a58454fc2512242d5ff69e9067afc926c3b563.camel@intel.com>
Subject: Re: [RFC PATCH v4 1/7] mm/demotion: Add support for explicit memory
 tiers
From:   Ying Huang <ying.huang@intel.com>
To:     Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>, linux-mm@kvack.org,
        akpm@linux-foundation.org
Cc:     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>
Date:   Wed, 08 Jun 2022 16:27:59 +0800
In-Reply-To: <b4ea5d02-40d9-9928-1094-9befed7ae4ff@linux.ibm.com>
References: <CAAPL-u-dFp7PwPH6DfbYdnY8xaGsHz3tRQ0CPGVkiqURvdN8=A@mail.gmail.com>
         <20220527122528.129445-1-aneesh.kumar@linux.ibm.com>
         <20220527122528.129445-2-aneesh.kumar@linux.ibm.com>
         <604403db000ced33f997688ce82eaa43ed6c8bbe.camel@intel.com>
         <b4ea5d02-40d9-9928-1094-9befed7ae4ff@linux.ibm.com>
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On Wed, 2022-06-08 at 13:54 +0530, Aneesh Kumar K V wrote:
> On 6/8/22 12:46 PM, Ying Huang wrote:
> > On Fri, 2022-05-27 at 17:55 +0530, Aneesh Kumar K.V wrote:
> > 
> > [snip]
> > 
> > > 
> > > +static int __init memory_tier_init(void)
> > > +{
> > > +	int ret;
> > > +
> > > +	ret = subsys_system_register(&memory_tier_subsys, memory_tier_attr_groups);
> > > +	if (ret)
> > > +		panic("%s() failed to register subsystem: %d\n", __func__, ret);
> > 
> > I don't think we should go panic for failing to register subsys and
> > device for memory tiers.  Just pr_err() should be enough.
> > 
> 
> So you are suggesting we continue to work with memory tiers with no 
> userspace interface?

Yes.  We don't need to panic system for this.

Best Regards,
Huang, Ying

> > > +
> > > +	/*
> > > +	 * Register only default memory tier to hide all empty
> > > +	 * memory tier from sysfs.
> > > +	 */
> > > +	ret = register_memory_tier(DEFAULT_MEMORY_TIER);
> > > +	if (ret)
> > > +		panic("%s() failed to register memory tier: %d\n", __func__, ret);
> > > +
> > > +	/*
> > > +	 * CPU only nodes are not part of memoty tiers.
> > > +	 */
> > > +	memory_tiers[DEFAULT_MEMORY_TIER]->nodelist = node_states[N_MEMORY];
> > > +
> > > +	return 0;
> > > +}
> > > +subsys_initcall(memory_tier_init);
> > > +
> > > +#endif	/* CONFIG_TIERED_MEMORY */
> > 
> > 
>