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Message-ID: <8a1e2bf5-1e6b-4142-b0ce-6b1bd3248956@intel.com>
Date: Tue, 15 Jul 2025 07:27:01 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: <babu.moger@....com>, Peter Newman <peternewman@...gle.com>
CC: <corbet@....net>, <tony.luck@...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
On 7/15/25 7:18 AM, Moger, Babu wrote:
> 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.
Not the first time:
https://lore.kernel.org/lkml/7fcdb142-b188-4f8d-ab26-391e0b9cec8e@intel.com/
Reinette
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