Message-ID: <d7dd2585-9f39-4e66-b218-4815bf888a77@amd.com>
Date: Wed, 17 Jul 2024 10:22:46 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
 fenghua.yu@...el.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, paulmck@...nel.org, rdunlap@...radead.org,
 tj@...nel.org, peterz@...radead.org, yanjiewtw@...il.com,
 kim.phillips@....com, lukas.bulwahn@...il.com, seanjc@...gle.com,
 jmattson@...gle.com, leitao@...ian.org, jpoimboe@...nel.org,
 rick.p.edgecombe@...el.com, kirill.shutemov@...ux.intel.com,
 jithu.joseph@...el.com, kai.huang@...el.com, kan.liang@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, pbonzini@...hat.com, sandipan.das@....com,
 ilpo.jarvinen@...ux.intel.com, peternewman@...gle.com,
 maciej.wieczor-retman@...el.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, eranian@...gle.com, james.morse@....com
Subject: Re: [PATCH v5 19/20] x86/resctrl: Introduce interface to list monitor
 states of all the groups

Hi Reinette,

On 7/12/24 17:16, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/3/24 2:48 PM, Babu Moger wrote:
>> Provide the interface to list the monitor states of all the resctrl
>> groups in ABMC mode.
>>
>> Example:
>> $cat /sys/fs/resctrl/info/L3_MON/mbm_control
>>
>> List follows the following format:
>>
>> "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>>
>> Format for specific type of groups:
>>
>> - Default CTRL_MON group:
>>    "//<domain_id>=<flags>"
>>
>> - Non-default CTRL_MON group:
>>    "<CTRL_MON group>//<domain_id>=<flags>"
>>
>> - Child MON group of default CTRL_MON group:
>>    "/<MON group>/<domain_id>=<flags>"
>>
>> - Child MON group of non-default CTRL_MON group:
>>    "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>>
>>
>> Flags can be one of the following:
>> t  MBM total event is enabled
>> l  MBM local event is enabled
>> tl Both total and local MBM events are enabled
>> _  None of the MBM events are enabled
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> v5: Replaced "assignment flags" with "flags".
>>      Changes related to mon structure.
>>      Changes related renaming the interface from mbm_assign_control to
>>      mbm_control.
>>
>> v4: Added functionality to query domain specific assigment in.
>>      rdtgroup_abmc_dom_state().
>>
>> v3: New patch.
>>      Addresses the feedback to provide the global assignment interface.
>>     
>> https://lore.kernel.org/lkml/c73f444b-83a1-4e9a-95d3-54c5165ee782@intel.com/
>> ---
>>   Documentation/arch/x86/resctrl.rst     |  54 ++++++++++
>>   arch/x86/kernel/cpu/resctrl/monitor.c  |   1 +
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 130 +++++++++++++++++++++++++
>>   3 files changed, 185 insertions(+)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst
>> b/Documentation/arch/x86/resctrl.rst
>> index 4c41c5622627..05fee779e109 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -304,6 +304,60 @@ with the following files:
>>   "num_mbm_cntrs":
>>       The number of monitoring counters available for assignment.
>>   +"mbm_control":
>> +    Available when ABMC features are supported.
> 
> "Available when ABMC features are supported." can be dropped
> 

Ok. Sure.

>> +    Reports the resctrl group and monitor status of each group.
>> +
>> +    List follows the following format:
>> +        "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>> +
>> +    Format for specific type of grpups:
> 
> grpups -> groups

Sure.

> 
>> +
>> +    * Default CTRL_MON group:
>> +        "//<domain_id>=<flags>"
>> +
>> +    * Non-default CTRL_MON group:
>> +        "<CTRL_MON group>//<domain_id>=<flags>"
>> +
>> +    * Child MON group of default CTRL_MON group:
>> +        "/<MON group>/<domain_id>=<flags>"
>> +
>> +    * Child MON group of non-default CTRL_MON group:
>> +        "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>> +
>> +    Flags can be one of the following:
>> +    ::
>> +
>> +     t  MBM total event is enabled.
>> +     l  MBM local event is enabled.
>> +     tl Both total and local MBM events are enabled.
>> +     _  None of the MBM events are enabled.
>> +
>> +    Examples:
>> +    ::
>> +
>> +     # mkdir /sys/fs/resctrl/mon_groups/child_default_mon_grp
>> +     # mkdir /sys/fs/resctrl/non_default_ctrl_mon_grp
>> +     # mkdir
>> /sys/fs/resctrl/non_default_ctrl_mon_grp/mon_groups/child_non_default_mon_grp
>> +
>> +     # cat /sys/fs/resctrl/info/L3_MON/mbm_control
>> +     non_default_ctrl_mon_grp//0=tl;1=tl;
>> +     non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
>> +     //0=tl;1=tl;
>> +     /child_default_mon_grp/0=tl;1=tl;
>> +
>> +     There are four resctrl groups. All the groups have total and local
>> events are
>> +     enabled on domain 0 and 1.
> 
> "All the groups have total and local events are enabled" -> "All the
> groups have total and local events enabled"?
> 

Sure.

>> +
> 
> The text below seems to repeat ealier description.

I can remove it.

> 
>> +     non_default_ctrl_mon_grp// - This is a non-default CTRL_MON group.
>> +
>> +     non_default_ctrl_mon_grp/child_non_default_mon_grp/ - This is a
>> child monitor
>> +     group of non-default CTRL_MON group.
>> +
>> +     // - This is a default CTRL_MON group.
>> +
>> +     /child_default_mon_grp/ - This is a child monitor group of default
>> CTRL_MON group.
>> +
>>   "max_threshold_occupancy":
>>           Read/write file provides the largest value (in
>>           bytes) at which a previously used LLC_occupancy
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c
>> b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index b96b0a8bd7d3..684730f1a72d 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -1244,6 +1244,7 @@ int __init rdt_get_mon_l3_config(struct
>> rdt_resource *r)
>>                   r->mon.num_mbm_cntrs = 64;
>>                 resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
>> +            resctrl_file_fflags_init("mbm_control", RFTYPE_MON_INFO);
> 
> Shouldn't this file always be present?
> 

This is only relevent when monitor assign features are supported.
Having the file without the feature is not usefull.


>>           }
>>       }
>>   diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index d978668c8865..0de9f23d5389 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -944,6 +944,130 @@ static ssize_t rdtgroup_mbm_mode_write(struct
>> kernfs_open_file *of,
>>       return ret ?: nbytes;
>>   }
>>   +static void rdtgroup_abmc_dom_cfg(void *info)
>> +{
>> +    u64 *msrval = info;
>> +
>> +    wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, *msrval);
>> +    rdmsrl(MSR_IA32_L3_QOS_ABMC_DSC, *msrval);
>> +}
>> +
>> +/*
>> + * Writing the counter id with CfgEn=0 on L3_QOS_ABMC_CFG and reading
>> + * L3_QOS_ABMC_DSC back will return configuration of the counter
>> + * specified.
> 
> Can this be expanded to explain what the return values mean?

Sure. Basically returns the counter id with its configuration.

Will add few more details.

> 
>> + */
>> +static int rdtgroup_abmc_dom_state(struct rdt_mon_domain *d, u32 cntr_id,
>> +                   u32 rmid)
>> +{
>> +    union l3_qos_abmc_cfg abmc_cfg = { 0 };
>> +
>> +    abmc_cfg.split.cfg_en = 0;
>> +    abmc_cfg.split.cntr_id = cntr_id;
>> +
>> +    smp_call_function_any(&d->hdr.cpu_mask, rdtgroup_abmc_dom_cfg,
>> +                  &abmc_cfg, 1);
>> +
>> +    if (abmc_cfg.split.cntr_en && abmc_cfg.split.bw_src == rmid)
>> +        return 0;
>> +    else
>> +        return -1;
>> +}
>> +
>> +static char *rdtgroup_mon_state_to_str(struct rdtgroup *rdtgrp,
>> +                       struct rdt_mon_domain *d, char *str)
>> +{
>> +    char *tmp = str;
>> +    int dom_state = ASSIGN_NONE;
> 
> reverse fir

Sure.

> 
>> +
>> +    /*
>> +     * Query the monitor state for the domain.
>> +     * Index 0 for evtid == QOS_L3_MBM_TOTAL_EVENT_ID
>> +     * Index 1 for evtid == QOS_L3_MBM_LOCAL_EVENT_ID
> 
> Why not use the helper?

Yes.

> 
>> +     */
>> +    if (rdtgrp->mon.cntr_id[0] != MON_CNTR_UNSET)
>> +        if (!rdtgroup_abmc_dom_state(d, rdtgrp->mon.cntr_id[0],
>> rdtgrp->mon.rmid))
>> +            dom_state |= ASSIGN_TOTAL;
>> +
>> +    if (rdtgrp->mon.cntr_id[1] != MON_CNTR_UNSET)
>> +        if (!rdtgroup_abmc_dom_state(d, rdtgrp->mon.cntr_id[1],
>> rdtgrp->mon.rmid))
>> +            dom_state |= ASSIGN_LOCAL;
>> +
>> +    switch (dom_state) {
>> +    case ASSIGN_NONE:
>> +        *tmp++ = '_';
>> +        break;
>> +    case (ASSIGN_TOTAL | ASSIGN_LOCAL):
>> +        *tmp++ = 't';
>> +        *tmp++ = 'l';
>> +        break;
>> +    case ASSIGN_TOTAL:
>> +        *tmp++ = 't';
>> +        break;
>> +    case ASSIGN_LOCAL:
>> +        *tmp++ = 'l';
>> +        break;
>> +    default:
>> +        break;
>> +    }
> 
> This switch statement does not scale. Adding new flags will be painful.
> Can flags not
> just incrementally be printed as learned from hardware with "_" printed as
> last resort?
> This would elimininate need for these "ASSIGN" flags.

Let me try to understand this.

You want to remove switch statement.

if (rdtgrp->mon.cntr_id[0] != MON_CNTR_UNSET)
   if (!rdtgroup_abmc_dom_state(d, rdtgrp->mon.cntr_id[0], rdtgrp->mon.rmid))
    *tmp++ = 't';

if (rdtgrp->mon.cntr_id[1] != MON_CNTR_UNSET)
   if (!rdtgroup_abmc_dom_state(d, rdtgrp->mon.cntr_id[1], rdtgrp->mon.rmid))
   *tmp++ = 'l';

If none of these flags are available, then
   *tmp++ = '_';

Is that the idea?

> 
>> +
>> +    *tmp = '\0';
>> +    return str;
>> +}
>> +
>> +static int rdtgroup_mbm_control_show(struct kernfs_open_file *of,
>> +                     struct seq_file *s, void *v)
>> +{
>> +    struct rdt_resource *r = of->kn->parent->priv;
>> +    struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>> +    struct rdt_mon_domain *dom;
>> +    struct rdtgroup *rdtg;
>> +    int grp_default = 0;
>> +    char str[10];
>> +
>> +    if (!hw_res->abmc_enabled) {
>> +        rdt_last_cmd_puts("ABMC feature is not enabled\n");
>> +        return -EINVAL;
>> +    }
>> +
>> +    mutex_lock(&rdtgroup_mutex);
>> +
>> +    list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list) {
>> +        struct rdtgroup *crg;
>> +
>> +        if (rdtg == &rdtgroup_default) {
>> +            grp_default = 1;
>> +            seq_puts(s, "//");
>> +        } else {
>> +            grp_default = 0;
>> +            seq_printf(s, "%s//", rdtg->kn->name);
>> +        }
> 
> Isn't the default resource group's name already empty string? That should
> eliminate the need for this special handling, no?

Yea. Let me try that.
> 
>> +
>> +        list_for_each_entry(dom, &r->mon_domains, hdr.list)
>> +            seq_printf(s, "%d=%s;", dom->hdr.id,
>> +                   rdtgroup_mon_state_to_str(rdtg, dom, str));
>> +        seq_putc(s, '\n');
>> +
>> +        list_for_each_entry(crg, &rdtg->mon.crdtgrp_list,
>> +                    mon.crdtgrp_list) {
>> +            if (grp_default)
>> +                seq_printf(s, "/%s/", crg->kn->name);
>> +            else
>> +                seq_printf(s, "%s/%s/", rdtg->kn->name,
>> +                       crg->kn->name);
>> +
> 
> Same here .... with default group having name of empty string it can just be
> printed directly, no?

Yea. Let me try that.

> 
>> +            list_for_each_entry(dom, &r->mon_domains, hdr.list)
>> +                seq_printf(s, "%d=%s;", dom->hdr.id,
>> +                       rdtgroup_mon_state_to_str(crg, dom, str));
>> +            seq_putc(s, '\n');
>> +        }
>> +    }
>> +
>> +    mutex_unlock(&rdtgroup_mutex);
>> +
>> +    return 0;
>> +}
>> +
>>   #ifdef CONFIG_PROC_CPU_RESCTRL
>>     /*
>> @@ -2156,6 +2280,12 @@ static struct rftype res_common_files[] = {
>>           .kf_ops        = &rdtgroup_kf_single_ops,
>>           .seq_show    = rdtgroup_num_mbm_cntrs_show,
>>       },
>> +    {
>> +        .name        = "mbm_control",
>> +        .mode        = 0444,
>> +        .kf_ops        = &rdtgroup_kf_single_ops,
>> +        .seq_show    = rdtgroup_mbm_control_show,
>> +    },
>>       {
>>           .name        = "cpus_list",
>>           .mode        = 0644,
> 
> Reinette
> 

-- 
Thanks
Babu Moger

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