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From: "Huang, Ying" <ying.huang@intel.com>
To: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Cc: Dan Williams <dan.j.williams@intel.com>,  <linux-cxl@vger.kernel.org>,
  <linux-kernel@vger.kernel.org>,  Andrew Morton
 <akpm@linux-foundation.org>,  Dave Jiang <dave.jiang@intel.com>,  Bharata
 B Rao <bharata@amd.com>,  "Alistair Popple" <apopple@nvidia.com>,  "Aneesh
 Kumar K . V" <aneesh.kumar@linux.ibm.com>
Subject: Re: [PATCH] cxl/region: Support to calculate memory tier abstract
 distance
In-Reply-To: <20240605131017.000069b6@Huawei.com> (Jonathan Cameron's message
	of "Wed, 5 Jun 2024 13:10:17 +0100")
References: <20240531024852.282767-1-ying.huang@intel.com>
	<20240605131017.000069b6@Huawei.com>
Date: Thu, 06 Jun 2024 09:14:45 +0800
Message-ID: <87a5jy98je.fsf@yhuang6-desk2.ccr.corp.intel.com>
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Hi, Jonathan,

Thank you very much for review!

Jonathan Cameron <Jonathan.Cameron@Huawei.com> writes:

> On Fri, 31 May 2024 10:48:52 +0800
> Huang Ying <ying.huang@intel.com> wrote:
>
>> To place memory nodes backed by CXL regions in the appropriate memory
>> tiers.  So that, pages can be promoted/demoted with the existing
>> memory tiering mechanism.
>> 
>> The abstract distance is calculated based on the memory access latency
>> and bandwidth of CXL regions.  Which in turn comes from the HMAT
>> and CDAT, etc.
>> 
>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> Cc: Dave Jiang <dave.jiang@intel.com>
>> Cc: Dan Williams <dan.j.williams@intel.com>
>> Cc: Bharata B Rao <bharata@amd.com>
>> Cc: Alistair Popple <apopple@nvidia.com>
>> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>
> Minor comments inline.  Otherwise, looks good to me.
>
> Jonathan
>
>
>> ---
>>  drivers/cxl/core/region.c | 40 +++++++++++++++++++++++++++++++++++----
>>  drivers/cxl/cxl.h         |  1 +
>>  2 files changed, 37 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index 00a9f0eef8dd..1f8f71a034ae 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -9,6 +9,7 @@
>>  #include <linux/uuid.h>
>>  #include <linux/sort.h>
>>  #include <linux/idr.h>
>> +#include <linux/memory-tiers.h>
>>  #include <cxlmem.h>
>>  #include <cxl.h>
>>  #include "core.h"
>> @@ -2304,14 +2305,20 @@ static bool cxl_region_update_coordinates(struct cxl_region *cxlr, int nid)
>>  	return true;
>>  }
>>  
>> +static int cxl_region_nid(struct cxl_region *cxlr)
>> +{
>> +	struct cxl_region_params *p = &cxlr->params;
>> +	struct cxl_endpoint_decoder *cxled = p->targets[0];
>> +	struct cxl_decoder *cxld = &cxled->cxld;
>> +
>> +	return phys_to_target_node(cxld->hpa_range.start);
>> +}
>> +
>>  static int cxl_region_perf_attrs_callback(struct notifier_block *nb,
>>  					  unsigned long action, void *arg)
>>  {
>>  	struct cxl_region *cxlr = container_of(nb, struct cxl_region,
>>  					       memory_notifier);
>> -	struct cxl_region_params *p = &cxlr->params;
>> -	struct cxl_endpoint_decoder *cxled = p->targets[0];
>> -	struct cxl_decoder *cxld = &cxled->cxld;
>>  	struct memory_notify *mnb = arg;
>>  	int nid = mnb->status_change_nid;
>>  	int region_nid;
>> @@ -2319,7 +2326,7 @@ static int cxl_region_perf_attrs_callback(struct notifier_block *nb,
>>  	if (nid == NUMA_NO_NODE || action != MEM_ONLINE)
>>  		return NOTIFY_DONE;
>>  
>> -	region_nid = phys_to_target_node(cxld->hpa_range.start);
>> +	region_nid = cxl_region_nid(cxlr);
>>  	if (nid != region_nid)
>>  		return NOTIFY_DONE;
>>  
>> @@ -2329,6 +2336,27 @@ static int cxl_region_perf_attrs_callback(struct notifier_block *nb,
>>  	return NOTIFY_OK;
>>  }
>>  
>> +static int cxl_region_calculate_adistance(struct notifier_block *nb,
>> +					  unsigned long nid, void *data)
>> +{
>> +	struct cxl_region *cxlr = container_of(nb, struct cxl_region,
>> +					       adist_notifier);
>> +	int region_nid;
>> +	struct access_coordinate *perf;
>> +	int *adist = data;
> Local style looks to be reverse xmas tree subject to any dependencies etc.

Sure.  Will change this to follow reverse xmas tree.

>> +
>> +	region_nid = cxl_region_nid(cxlr);
>> +	if (nid != region_nid)
>> +		return NOTIFY_OK;
>> +
>> +	perf = &cxlr->coord[ACCESS_COORDINATE_CPU];
>> +
>> +	if (mt_perf_to_adistance(perf, adist))
>> +		return NOTIFY_OK;
>> +
>> +	return NOTIFY_STOP;
>> +}
>> +
>>  /**
>>   * devm_cxl_add_region - Adds a region to a decoder
>>   * @cxlrd: root decoder
>> @@ -2380,6 +2408,10 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
>>  	cxlr->memory_notifier.priority = CXL_CALLBACK_PRI;
>>  	register_memory_notifier(&cxlr->memory_notifier);
>>  
>> +	cxlr->adist_notifier.notifier_call = cxl_region_calculate_adistance;
>> +	cxlr->adist_notifier.priority = 100;
>> +	register_mt_adistance_algorithm(&cxlr->adist_notifier);
>> +
>>  	rc = devm_add_action_or_reset(port->uport_dev, unregister_region, cxlr);
>>  	if (rc)
>>  		return ERR_PTR(rc);
>> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
>> index 603c0120cff8..6891f87f8ef7 100644
>> --- a/drivers/cxl/cxl.h
>> +++ b/drivers/cxl/cxl.h
>> @@ -534,6 +534,7 @@ struct cxl_region {
> This has docs that need an updte.

Yes.  Thanks for reminding!

>>  	struct cxl_region_params params;
>>  	struct access_coordinate coord[ACCESS_COORDINATE_MAX];
>>  	struct notifier_block memory_notifier;
>> +	struct notifier_block adist_notifier;
>>  };
>>  
>>  struct cxl_nvdimm_bridge {

--
Best Regards,
Huang, Ying