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Message-ID: <40ff2cd0-c8b9-460b-b98a-087cb251324e@amd.com>
Date: Wed, 28 May 2025 11:56:36 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
Babu Moger <babu.moger@....com>, corbet@....net, tony.luck@...el.com,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com
Cc: james.morse@....com, dave.martin@....com, fenghuay@...dia.com,
x86@...nel.org, hpa@...or.com, paulmck@...nel.org,
akpm@...ux-foundation.org, thuth@...hat.com, rostedt@...dmis.org,
ardb@...nel.org, gregkh@...uxfoundation.org, daniel.sneddon@...ux.intel.com,
jpoimboe@...nel.org, alexandre.chartre@...cle.com,
pawan.kumar.gupta@...ux.intel.com, thomas.lendacky@....com,
perry.yuan@....com, seanjc@...gle.com, kai.huang@...el.com,
xiaoyao.li@...el.com, kan.liang@...ux.intel.com, xin3.li@...el.com,
ebiggers@...gle.com, xin@...or.com, sohil.mehta@...el.com,
andrew.cooper3@...rix.com, mario.limonciello@....com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
peternewman@...gle.com, maciej.wieczor-retman@...el.com, eranian@...gle.com,
Xiaojian.Du@....com, gautham.shenoy@....com
Subject: Re: [PATCH v13 08/27] x86/resctrl: Introduce mbm_cntr_cfg to track
assignable counters at domain
Hi Reinette,
On 5/22/2025 4:02 PM, Reinette Chatre wrote:
> Hi Babu,
>
> shortlog: "at domain" -> "per domain"?
>
Sure.
> On 5/15/25 3:51 PM, Babu Moger wrote:
>> In mbm_cntr_assign mode hardware counters are assigned/unassigned to an
>> MBM event of a monitor group. Hardware counters are assigned/unassigned
>> at monitoring domain level.
>>
>> Manage a monitoring domain's hardware counters using a per monitoring
>> domain array of struct mbm_cntr_cfg that is indexed by the hardware
>> counter ID. A hardware counter's configuration contains the MBM event
>> ID and points to the monitoring group that it is assigned to, with a
>> NULL pointer meaning that the hardware counter is available for assignment.
>>
>> There is no direct way to determine which hardware counters are assigned
>> to a particular monitoring group. Check every entry of every hardware
>> counter configuration array in every monitoring domain to query which
>> MBM events of a monitoring group is tracked by hardware. Such queries are
>> acceptable because of a very small number of assignable counters (32
>> to 64).
>>
>> Suggested-by: Peter Newman <peternewman@...gle.com>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> v13: Resolved conflicts caused by the recent FS/ARCH code restructure.
>> The files monitor.c/rdtgroup.c have been split between FS and ARCH directories.
>>
>> v12: Fixed the struct mbm_cntr_cfg code documentation.
>> Removed few strange charactors in changelog.
>> Added the counter range for better understanding.
>> Moved the struct mbm_cntr_cfg definition to resctrl/internal.h as
>> suggested by James.
>>
>> v11: Refined the change log based on Reinette's feedback.
>> Fixed few style issues.
>>
>> v10: Patch changed completely to handle the counters at domain level.
>> https://lore.kernel.org/lkml/CALPaoCj+zWq1vkHVbXYP0znJbe6Ke3PXPWjtri5AFgD9cQDCUg@mail.gmail.com/
>> Removed Reviewed-by tag.
>> Did not see the need to add cntr_id in mbm_state structure. Not used in the code.
>>
>> v9: Added Reviewed-by tag. No other changes.
>>
>> v8: Minor commit message changes.
>>
>> v7: Added check mbm_cntr_assignable for allocating bitmap mbm_cntr_map
>>
>> v6: New patch to add domain level assignment.
>> ---
>> fs/resctrl/rdtgroup.c | 11 +++++++++++
>> include/linux/resctrl.h | 16 ++++++++++++++++
>> 2 files changed, 27 insertions(+)
>>
>> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
>> index 51f8f8d3ccbc..e2005fc9acd9 100644
>> --- a/fs/resctrl/rdtgroup.c
>> +++ b/fs/resctrl/rdtgroup.c
>> @@ -4085,6 +4085,7 @@ static void rdtgroup_setup_default(void)
>>
>> static void domain_destroy_mon_state(struct rdt_mon_domain *d)
>> {
>> + kfree(d->cntr_cfg);
>> bitmap_free(d->rmid_busy_llc);
>> kfree(d->mbm_total);
>> kfree(d->mbm_local);
>> @@ -4171,6 +4172,16 @@ static int domain_setup_mon_state(struct rdt_resource *r, struct rdt_mon_domain
>> return -ENOMEM;
>> }
>> }
>> + if (resctrl_is_mbm_enabled() && r->mon.mbm_cntr_assignable) {
>> + tsize = sizeof(*d->cntr_cfg);
>> + d->cntr_cfg = kcalloc(r->mon.num_mbm_cntrs, tsize, GFP_KERNEL);
>> + if (!d->cntr_cfg) {
>> + bitmap_free(d->rmid_busy_llc);
>> + kfree(d->mbm_total);
>> + kfree(d->mbm_local);
>> + return -ENOMEM;
>> + }
>> + }
>>
>> return 0;
>> }
>> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
>> index bdb264875ef6..d77981d1fcb9 100644
>> --- a/include/linux/resctrl.h
>> +++ b/include/linux/resctrl.h
>> @@ -156,6 +156,20 @@ struct rdt_ctrl_domain {
>> u32 *mbps_val;
>> };
>>
>> +/**
>> + * struct mbm_cntr_cfg - Assignable counter configuration
>> + * @evtid: MBM event to which the counter is assigned. Only valid
>> + * if @rdtgroup is not NULL.
>> + * @evt_cfg: Event configuration value.
>
> @evt_cfg is not introduced in changelog nor defined here. Please add a snippet here
> on what @evt_cfg's values represent. This is important since this is exposed
> as resctrl fs API to architectures so all architectures need to use same values when
> interacting with resctrl.
Sure.
@evt_cfg: A value that represents memory transactions (e.g., reads,
writes, etc.).
>
>> + * @rdtgrp: resctrl group assigned to the counter. NULL if the
>> + * counter is free.
>> + */
>> +struct mbm_cntr_cfg {
>> + enum resctrl_event_id evtid;
>> + u32 evt_cfg;
>> + struct rdtgroup *rdtgrp;
>
> Please align struct member names using TABs.
Sure.
>
>> +};
>> +
>> /**
>> * struct rdt_mon_domain - group of CPUs sharing a resctrl monitor resource
>> * @hdr: common header for different domain types
>> @@ -167,6 +181,7 @@ struct rdt_ctrl_domain {
>> * @cqm_limbo: worker to periodically read CQM h/w counters
>> * @mbm_work_cpu: worker CPU for MBM h/w counters
>> * @cqm_work_cpu: worker CPU for CQM h/w counters
>> + * @cntr_cfg: assignable counters configuration
>
> "array of assignable counters' configuration (indexed by counter ID)"
Sure.
>
>> */
>> struct rdt_mon_domain {
>> struct rdt_domain_hdr hdr;
>> @@ -178,6 +193,7 @@ struct rdt_mon_domain {
>> struct delayed_work cqm_limbo;
>> int mbm_work_cpu;
>> int cqm_work_cpu;
>> + struct mbm_cntr_cfg *cntr_cfg;
>> };
>>
>> /**
>
> Reinette
>
thanks
Babu
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