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Message-ID: <cf9e1e9f-7d54-4eff-aac2-1bc5c4ec4f82@intel.com>
Date: Thu, 28 Aug 2025 20:11:00 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Moger, Babu" <babu.moger@....com>, <corbet@....net>,
<tony.luck@...el.com>, <Dave.Martin@....com>, <james.morse@....com>,
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Subject: Re: [PATCH v8 10/10] fs/resctrl: Update bit_usage to reflect io_alloc
Hi Babu,
On 8/26/25 3:51 PM, Moger, Babu wrote:
> 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.
This sounds as though when a bit is set in io_alloc_cbm then its corresponding position
will contain an "X". An "X" will only be displayed if io_alloc_cbm has the corresponding
bit set *and* the bit appears in a resource group's allocation.
I think that patch #7 adds a very good definition of io_alloc_cbm and that it is
unnecessary to duplicate it. Simply referring to io_alloc_cbm should thus be fine with
user's search for it in the doc leading to a good description.
Considering this, how about just:
"X":
Corresponding region is available for sharing and
used by hardware and software. These are the
bits that appear in "shareable_bits" or "io_alloc_cbm" as
well as a resource group's allocation.
Please also update the "H" section.
Reinette
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