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Message-ID: <3cf90472-be2d-4800-b3d2-879b5fca2012@intel.com>
Date: Thu, 17 Jul 2025 20:56:48 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
<james.morse@....com>, <tglx@...utronix.de>, <mingo@...hat.com>,
<bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <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>,
<peternewman@...gle.com>, <eranian@...gle.com>
Subject: Re: [PATCH v15 29/34] x86,fs/resctrl: Auto assign counters on mkdir
and clean up on group removal
Hi Babu,
On 7/8/25 3:17 PM, Babu Moger wrote:
> Resctrl provides a user-configurable option mbm_assign_on_mkdir that
> determines if a counter will automatically be assigned to an RMID, event
> pair when its associated monitor group is created via mkdir.
>
> Enable mbm_assign_on_mkdir by default and automatically assign the counters
> when a resctrl group is created.
>
> Counters allocated to a resctrl group should be released when the group is
> deleted. Add support to unassign and free counters during the group
> teardown.
>
> By default, each group requires two counters: one for the MBM total event
> and one for the MBM local event.
>
> If the counters are exhausted, the kernel will log the error message
> "Unable to allocate counter in domain" in
> /sys/fs/resctrl/info/last_cmd_status when a new group is created and the
> counter assignment will fail. However, the creation of a group should not
> fail due to assignment failures. Users have the flexibility to modify the
> assignments at a later time.
I find that this changelog jumps around a bit. Below is an attempt at some
re-organization. Please feel free to improve:
Resctrl provides a user-configurable option mbm_assign_on_mkdir that
determines if a counter will automatically be assigned to an RMID, event
pair when its associated monitor group is created via mkdir.
Enable mbm_assign_on_mkdir by default to automatically assign
counters to the two default events (MBM total and MBM local) of a new
monitoring group created via mkdir. This maintains backward compatibility
with original resctrl support for these two events.
Unassign and free counters belonging to a monitoring group when the group is
deleted.
Monitor group creation does not fail if a counter cannot be assigned to
one or both events. There may be limited counters and users have the
flexibility to modify counter assignments at a later time.
Log the error message "Unable to allocate counter in domain" in
/sys/fs/resctrl/info/last_cmd_status when a new monitoring group is created
but counter assignment failed.
>
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
...
> ---
> arch/x86/kernel/cpu/resctrl/monitor.c | 1 +
> fs/resctrl/rdtgroup.c | 70 ++++++++++++++++++++++++++-
> 2 files changed, 69 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 026c2e2d19d3..e0706083fe0e 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -457,6 +457,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
> r->mon.mbm_cntr_assignable = true;
> cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
> r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1;
> + r->mon.mbm_assign_on_mkdir = true;
This is a resctrl fs default. Should it not be set in
resctrl_mon_resource_init()?
> }
>
> r->mon_capable = true;
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index b7289ce2b3a6..645245f274e9 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -2884,6 +2884,54 @@ static void schemata_list_destroy(void)
> }
> }
>
> +/*
> + * rdtgroup_assign_cntrs() - Assign counters to MBM events. Called when
> + * a new group is created.
> + * If "mbm_event" counter assignment mode is enabled, counters should be
> + * automatically assigned if the "mbm_assign_on_mkdir" is set.
> + * Each group can accommodate two counters: one for the total event and
"Each group can accommodate two counters" -> "Each group can accommodate two counters
per domain"?
> + * one for the local event. Assignments may fail due to the limited number
> + * of counters. However, it is not necessary to fail the group creation
> + * and thus no failure is returned. Users have the option to modify the
> + * counter assignments after the group has been created.
> + */
> +static void rdtgroup_assign_cntrs(struct rdtgroup *rdtgrp)
> +{
> + struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
> +
> + if (!r->mon_capable || !resctrl_arch_mbm_cntr_assign_enabled(r) ||
> + !r->mon.mbm_assign_on_mkdir)
> + return;
> +
> + if (resctrl_is_mon_event_enabled(QOS_L3_MBM_TOTAL_EVENT_ID))
> + rdtgroup_assign_cntr_event(NULL, rdtgrp,
> + &mon_event_all[QOS_L3_MBM_TOTAL_EVENT_ID]);
> +
> + if (resctrl_is_mon_event_enabled(QOS_L3_MBM_LOCAL_EVENT_ID))
> + rdtgroup_assign_cntr_event(NULL, rdtgrp,
> + &mon_event_all[QOS_L3_MBM_LOCAL_EVENT_ID]);
> +}
> +
Reinette
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