Re: [PATCH v8 10/10] fs/resctrl: Update bit_usage to reflect io_alloc

["Moger, Babu" <babu.moger@amd.com>]

Hi Reinette,

On 8/7/2025 8:54 PM, Reinette Chatre wrote:
> Hi Babu
>
> On 8/5/25 4:30 PM, Babu Moger wrote:
>> When the io_alloc feature is enabled, a portion of the cache can be
>> configured for shared use between hardware and software.
>>
>> Update the bit_usage representation to reflect the io_alloc configuration.
> ... but no update to the bit_usage docs :(


Yes. Missed that.  Will update the text.


>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
> ..
>
>> ---
>>   Documentation/filesystems/resctrl.rst | 19 +++++++++++++------
>>   fs/resctrl/ctrlmondata.c              |  2 +-
>>   fs/resctrl/internal.h                 |  2 ++
>>   fs/resctrl/rdtgroup.c                 | 18 ++++++++++++++++--
>>   4 files changed, 32 insertions(+), 9 deletions(-)
>>
>> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
>> index d955e8525af0..1e46231b929c 100644
>> --- a/Documentation/filesystems/resctrl.rst
>> +++ b/Documentation/filesystems/resctrl.rst
>> @@ -90,12 +90,19 @@ related to allocation:
>>   		must be set when writing a mask.
>>   
>>   "shareable_bits":
>> -		Bitmask of shareable resource with other executing
>> -		entities (e.g. I/O). User can use this when
>> -		setting up exclusive cache partitions. Note that
>> -		some platforms support devices that have their
>> -		own settings for cache use which can over-ride
>> -		these bits.
>> +		Bitmask of shareable resource with other executing entities
>> +		(e.g. I/O). Applies to all instances of this resource. User
>> +		can use this when setting up exclusive cache partitions.
>> +		Note that some platforms support devices that have their
>> +		own settings for cache use which can over-ride these bits.
>> +
>> +		When "io_alloc" is enabled, a portion of each cache instance can
>> +		be configured for shared use between hardware and software.
>> +		"bit_usage" should be used to see which portions of each cache
>> +		instance is configured for hardware use via "io_alloc" feature
>> +		because every cache instance can have its "io_alloc" bitmask
>> +		configured independently via io_alloc_cbm.
>> +
>>   "bit_usage":
> More ignored feedback. I was expecting changes to the "bit_usage" section.
> https://lore.kernel.org/lkml/94d075e0-6703-449f-9c0c-8e5973349dff@intel.com/

Yea.  Added following text now.


diff --git a/Documentation/filesystems/resctrl.rst 
b/Documentation/filesystems/resctrl.rst
index 273c9c9389a4..0a56829407c9 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -124,8 +124,11 @@ related to allocation:
                         "X":
                               Corresponding region is available for 
sharing and
                               used by hardware and software. These are the
-                             bits that appear in "shareable_bits" as
-                             well as a resource group's allocation.
+                             bits that appear in "shareable_bits" as 
well as a
+                             resource group's allocation. When io_alloc 
is enabled,
+                             the capacity bitmasks configured via 
io_alloc_cbm will
+                             also appear here, indicating the cache 
regions shared
+                             with I/O devices.
                         "S":
                               Corresponding region is used by software
                               and available for sharing.


>
>>   		Annotated capacity bitmasks showing how all
>>   		instances of the resource are used. The legend is:
>> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
>> index 1f69117f96f8..cfa766319189 100644
>> --- a/fs/resctrl/ctrlmondata.c
>> +++ b/fs/resctrl/ctrlmondata.c
>> @@ -754,7 +754,7 @@ static int resctrl_io_alloc_init_cbm(struct resctrl_schema *s, u32 closid)
>>    * resource. Note that if Code Data Prioritization (CDP) is enabled, the number
>>    * of available CLOSIDs is reduced by half.
>>    */
>> -static u32 resctrl_io_alloc_closid(struct rdt_resource *r)
>> +u32 resctrl_io_alloc_closid(struct rdt_resource *r)
>>   {
>>   	if (resctrl_arch_get_cdp_enabled(r->rid))
>>   		return resctrl_arch_get_num_closid(r) / 2  - 1;
>> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
>> index 5467c3ad1b6d..98b87725508b 100644
>> --- a/fs/resctrl/internal.h
>> +++ b/fs/resctrl/internal.h
>> @@ -395,6 +395,8 @@ int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
>>   ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of, char *buf,
>>   				   size_t nbytes, loff_t off);
>>   
>> +u32 resctrl_io_alloc_closid(struct rdt_resource *r);
>> +
>>   const char *rdtgroup_name_by_closid(int closid);
>>   
>>   #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
>> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
>> index a3ab2851c6da..b85c2622c94b 100644
>> --- a/fs/resctrl/rdtgroup.c
>> +++ b/fs/resctrl/rdtgroup.c
>> @@ -1068,15 +1068,17 @@ static int rdt_bit_usage_show(struct kernfs_open_file *of,
>>   
>>   	cpus_read_lock();
>>   	mutex_lock(&rdtgroup_mutex);
>> -	hw_shareable = r->cache.shareable_bits;
>>   	list_for_each_entry(dom, &r->ctrl_domains, hdr.list) {
>>   		if (sep)
>>   			seq_putc(seq, ';');
>> +		hw_shareable = r->cache.shareable_bits;
>>   		sw_shareable = 0;
>>   		exclusive = 0;
>>   		seq_printf(seq, "%d=", dom->hdr.id);
>>   		for (i = 0; i < closids_supported(); i++) {
>> -			if (!closid_allocated(i))
>> +			if (!closid_allocated(i) ||
>> +			    (resctrl_arch_get_io_alloc_enabled(r) &&
>> +			     i == resctrl_io_alloc_closid(r)))
>>   				continue;
>>   			ctrl_val = resctrl_arch_get_config(r, dom, i,
>>   							   s->conf_type);
>> @@ -1104,6 +1106,18 @@ static int rdt_bit_usage_show(struct kernfs_open_file *of,
>>   				break;
>>   			}
>>   		}
>> +
>> +		/*
>> +		 * When the "io_alloc" feature is enabled, a portion of the
>> +		 * cache is configured for shared use between hardware and software.
> Please add snippet to comment that highlights that CBM of CDP peers are kept in sync and the
> CBM used for I/O can thus be obtained from either.


Sure. Thanks

Babu