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Message-ID: <bdda1774-e03b-44eb-905d-1ca2e30ab61d@amd.com>
Date: Tue, 15 Jul 2025 09:18:53 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Peter Newman <peternewman@...gle.com>
Cc: corbet@....net, tony.luck@...el.com, reinette.chatre@...el.com,
james.morse@....com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, Dave.Martin@....com, 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, jpoimboe@...nel.org,
pawan.kumar.gupta@...ux.intel.com, xin@...or.com, manali.shukla@....com,
tao1.su@...ux.intel.com, sohil.mehta@...el.com, kai.huang@...el.com,
xiaoyao.li@...el.com, peterz@...radead.org, xin3.li@...el.com,
kan.liang@...ux.intel.com, mario.limonciello@....com,
thomas.lendacky@....com, perry.yuan@....com, gautham.shenoy@....com,
chang.seok.bae@...el.com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, eranian@...gle.com
Subject: Re: [PATCH v15 28/34] fs/resctrl: Introduce mbm_assign_on_mkdir to
enable assignments on mkdir
Hi Peter,
On 7/15/25 08:53, Peter Newman wrote:
> Hi Babu,
>
> On Wed, Jul 9, 2025 at 12:22 AM Babu Moger <babu.moger@....com> wrote:
>>
>> The "mbm_event" counter assignment mode allows users to assign a hardware
>> counter to an RMID, event pair and monitor the bandwidth as long as it is
>> assigned.
>>
>> Introduce a user-configurable option that determines if a counter will
>> automatically be assigned to an RMID, event pair when its associated
>> monitor group is created via mkdir.
>>
>> Suggested-by: Peter Newman <peternewman@...gle.com>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> v15: Fixed the static checker warning in resctrl_mbm_assign_on_mkdir_write() reported in
>> https://lore.kernel.org/lkml/dd4a1021-b996-438e-941c-69dfcea5f22a@intel.com/
>>
>> v14: Added rdtgroup_mutex in resctrl_mbm_assign_on_mkdir_show().
>> Updated resctrl.rst for clarity.
>> Fixed squashing of few previous changes.
>> Added more code documentation.
>>
>> v13: Added Suggested-by tag.
>> Resolved conflicts caused by the recent FS/ARCH code restructure.
>> The rdtgroup.c/monitor.c file has now been split between the FS and ARCH directories.
>>
>> v12: New patch. Added after the discussion on the list.
>> https://lore.kernel.org/lkml/CALPaoCh8siZKjL_3yvOYGL4cF_n_38KpUFgHVGbQ86nD+Q2_SA@mail.gmail.com/
>> ---
>> Documentation/filesystems/resctrl.rst | 16 ++++++++++
>> fs/resctrl/monitor.c | 2 ++
>> fs/resctrl/rdtgroup.c | 43 +++++++++++++++++++++++++++
>> include/linux/resctrl.h | 3 ++
>> 4 files changed, 64 insertions(+)
>>
>> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
>> index 06c8c08d0341..f9e9a8a66cae 100644
>> --- a/Documentation/filesystems/resctrl.rst
>> +++ b/Documentation/filesystems/resctrl.rst
>> @@ -354,6 +354,22 @@ with the following files:
>> # cat /sys/fs/resctrl/info/L3_MON/event_configs/mbm_total_bytes/event_filter
>> local_reads,local_non_temporal_writes
>>
>> +"mbm_assign_on_mkdir":
>> + Determines if a counter will automatically be assigned to an RMID, event pair
>> + when its associated monitor group is created via mkdir. It is enabled by default
>> + on boot and users can disable by writing to the interface.
>> +
>> + "0":
>> + Auto assignment is disabled.
>> + "1":
>> + Auto assignment is enabled.
>> +
>> + Example::
>> +
>> + # echo 0 > /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir
>> + # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_on_mkdir
>> + 0
>> +
>> "max_threshold_occupancy":
>> Read/write file provides the largest value (in
>> bytes) at which a previously used LLC_occupancy
>> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
>> index 0722e72f6cb1..ccca2330eebd 100644
>> --- a/fs/resctrl/monitor.c
>> +++ b/fs/resctrl/monitor.c
>> @@ -984,6 +984,8 @@ int resctrl_mon_resource_init(void)
>> resctrl_file_fflags_init("available_mbm_cntrs",
>> RFTYPE_MON_INFO | RFTYPE_RES_CACHE);
>> resctrl_file_fflags_init("event_filter", RFTYPE_ASSIGN_CONFIG);
>> + resctrl_file_fflags_init("mbm_assign_on_mkdir", RFTYPE_MON_INFO |
>> + RFTYPE_RES_CACHE);
>> }
>>
>> return 0;
>> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
>> index 4889e7556cc7..b7289ce2b3a6 100644
>> --- a/fs/resctrl/rdtgroup.c
>> +++ b/fs/resctrl/rdtgroup.c
>> @@ -1987,6 +1987,42 @@ static ssize_t event_filter_write(struct kernfs_open_file *of, char *buf,
>> return ret ?: nbytes;
>> }
>>
>> +static int resctrl_mbm_assign_on_mkdir_show(struct kernfs_open_file *of,
>> + struct seq_file *s, void *v)
>> +{
>> + struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
>> +
>> + mutex_lock(&rdtgroup_mutex);
>> + rdt_last_cmd_clear();
>> +
>> + seq_printf(s, "%u\n", r->mon.mbm_assign_on_mkdir);
>> +
>> + mutex_unlock(&rdtgroup_mutex);
>> +
>> + return 0;
>> +}
>> +
>> +static ssize_t resctrl_mbm_assign_on_mkdir_write(struct kernfs_open_file *of,
>> + char *buf, size_t nbytes, loff_t off)
>> +{
>> + struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
>> + bool value;
>> + int ret;
>> +
>> + ret = kstrtobool(buf, &value);
>> + if (ret)
>> + return ret;
>> +
>> + mutex_lock(&rdtgroup_mutex);
>> + rdt_last_cmd_clear();
>> +
>> + r->mon.mbm_assign_on_mkdir = value;
>> +
>> + mutex_unlock(&rdtgroup_mutex);
>> +
>> + return 0;
>
> I noticed that "echo 0 > mbm_assign_on_mkdir" never completes. This
> should return nbytes.
>
Agree. Thanks for pointing it out.
--
Thanks
Babu Moger
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