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Message-ID: <4145a0fc-138a-4a96-879d-34b07fd169a9@amd.com>
Date: Tue, 26 Aug 2025 17:51:21 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
tony.luck@...el.com, Dave.Martin@....com, james.morse@....com,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, akpm@...ux-foundation.org,
paulmck@...nel.org, rostedt@...dmis.org, Neeraj.Upadhyay@....com,
david@...hat.com, arnd@...db.de, fvdl@...gle.com, seanjc@...gle.com,
thomas.lendacky@....com, pawan.kumar.gupta@...ux.intel.com,
yosry.ahmed@...ux.dev, sohil.mehta@...el.com, xin@...or.com,
kai.huang@...el.com, xiaoyao.li@...el.com, peterz@...radead.org,
me@...aill.net, mario.limonciello@....com, xin3.li@...el.com,
ebiggers@...gle.com, ak@...ux.intel.com, chang.seok.bae@...el.com,
andrew.cooper3@...rix.com, perry.yuan@....com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, manali.shukla@....com, gautham.shenoy@....com
Subject: Re: [PATCH v8 10/10] fs/resctrl: Update bit_usage to reflect io_alloc
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@....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
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