Re: [PATCH v3 2/3] cxl/region: Support to calculate memory tier abstract distance

[fan <nifan.cxl@gmail.com>]

On Tue, Jun 18, 2024 at 04:46:38PM +0800, Huang Ying wrote:
> An abstract distance value must be assigned by the driver that makes
> the memory available to the system. It reflects relative performance
> and is used to place memory nodes backed by CXL regions in the appropriate
> memory tiers allowing promotion/demotion within the existing memory tiering
> mechanism.
> 
> The abstract distance is calculated based on the memory access latency
> and bandwidth of CXL regions.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Acked-by: Dan Williams <dan.j.williams@intel.com>
> Cc: Alison Schofield <alison.schofield@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Dave Jiang <dave.jiang@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>
> Cc: Davidlohr Bueso <dave@stgolabs.net>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> ---

Reviewed-by: Fan Ni <fan.ni@samsung.com>

>  drivers/cxl/core/region.c | 27 +++++++++++++++++++++++++++
>  drivers/cxl/cxl.h         |  2 ++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 51aeef2c012c..dc15ceba7ab7 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"
> @@ -2228,6 +2229,7 @@ static void unregister_region(void *_cxlr)
>  	int i;
>  
>  	unregister_memory_notifier(&cxlr->memory_notifier);
> +	unregister_mt_adistance_algorithm(&cxlr->adist_notifier);
>  	device_del(&cxlr->dev);
>  
>  	/*
> @@ -2340,6 +2342,27 @@ 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);
> +	struct access_coordinate *perf;
> +	int *adist = data;
> +	int region_nid;
> +
> +	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
> @@ -2382,6 +2405,10 @@ 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..f46252373159 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -522,6 +522,7 @@ struct cxl_region_params {
>   * @params: active + config params for the region
>   * @coord: QoS access coordinates for the region
>   * @memory_notifier: notifier for setting the access coordinates to node
> + * @adist_notifier: notifier for calculating the abstract distance of node
>   */
>  struct cxl_region {
>  	struct device dev;
> @@ -534,6 +535,7 @@ struct cxl_region {
>  	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 {
> -- 
> 2.39.2
>