Re: [PATCH v3 09/10] x86/resctrl: Add sysfs interface to write the event configuration

[Moger, Babu]

On 8/24/22 16:16, Reinette Chatre wrote:
> Hi Babu,
>
> On 8/22/2022 6:44 AM, Babu Moger wrote:
>> Add the sysfs interface to write the event configuration for the
>> MBM configurable events. The event configuration can be changed by
>> writing to the sysfs file for that specific event.
>>
>> Following are the types of events supported.
>> ==================================================================
>> Bits    Description
>> 6       Dirty Victims from the QOS domain to all types of memory
>> 5       Reads to slow memory in the non-local NUMA domain
>> 4       Reads to slow memory in the local NUMA domain
>> 3       Non-temporal writes to non-local NUMA domain
>> 2       Non-temporal writes to local NUMA domain
>> 1       Reads to memory in the non-local NUMA domain
>> 0       Reads to memory in the local NUMA domain
>>
>> By default the mbm_total_bytes configuration is set to 0x7f to count
>> all the types of events and mbm_local_bytes configuration is set to
>> 0x15 to count all the local memory events.
>>
>> For example:
>> To change the mbm_total_bytes to count all the reads, run the command.
>> $echo  0x33 > /sys/fs/resctrl/mon_data/mon_L3_00/mbm_total_config
>>
>> To change the mbm_local_bytes to count all the slow memory reads, run
>> the command.
>> $echo  0x30 > /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_config
>>
>> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
>> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>
>> ---
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |  109 ++++++++++++++++++++++++++++++++
>>  1 file changed, 109 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index e1847d49fa15..83c8780726ff 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -323,9 +323,118 @@ int rdtgroup_mondata_config_show(struct seq_file *m, void *arg)
>>  	return ret;
>>  }
>>  
>> +/*
>> + * This is called via IPI to read the CQM/MBM counters
>> + * in a domain.
>> + */
>> +void mon_event_config_write(void *info)
>> +{
>> +	union mon_data_bits *md = info;
>> +	u32 evtid = md->u.evtid;
>> +	u32 msr_index;
>> +
>> +	switch (evtid) {
>> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
>> +		msr_index = 0;
>> +		break;
>> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
>> +		msr_index = 1;
>> +		break;
>> +	default:
>> +		return; /* Not expected to come here */
> Please no inline comments.
Ok sure.
>
>> +	}
>> +
>> +	wrmsr(MSR_IA32_EVT_CFG_BASE + msr_index, md->u.mon_config, 0);
>> +}
>> +
>> +ssize_t  rdtgroup_mondata_config_write(struct kernfs_open_file *of,
>> +				       char *buf, size_t nbytes, loff_t off)
>> +{
>> +	struct rdt_hw_resource *hw_res;
>> +	struct rdtgroup *rdtgrp;
>> +	struct rdt_resource *r;
>> +	unsigned int mon_config;
>> +	cpumask_var_t cpu_mask;
>> +	union mon_data_bits md;
>> +	struct rdt_domain *d;
>> +	u32 resid, domid;
>> +	int ret = 0, cpu;
>> +
>> +	ret = kstrtouint(buf, 0, &mon_config);
>> +	if (ret)
>> +		return ret;
>> +
>> +	rdt_last_cmd_clear();
>> +
>> +	/* mon_config cannot be more than the supported set of events */
>> +	if (mon_config > GENMASK(6, 0)) {
> Could this "GENMASK()" be given a name and be moved closer to where
> the bits are defined in internal.h? This will be easier to read and if any
> new bits are added it would hopefully be noticed more easily to get
> an update also.
Ok. Sure..
>
>> +		rdt_last_cmd_puts("Invalid event configuration\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	cpus_read_lock();
>> +	rdtgrp = rdtgroup_kn_lock_live(of->kn);
>> +	if (!rdtgrp) {
>> +		return -ENOENT;
>> +		goto e_unlock;
>> +	}
>> +
>> +	if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL)) {
>> +		ret = -ENOMEM;
>> +		goto e_unlock;
>> +	}
>> +
>> +
>> +	md.priv = of->kn->priv;
>> +	resid = md.u.rid;
>> +	domid = md.u.domid;
>> +
>> +	hw_res = &rdt_resources_all[resid];
>> +	r = &hw_res->r_resctrl;
>> +	d = rdt_find_domain(r, domid, NULL);
>> +	if (IS_ERR_OR_NULL(d)) {
>> +		ret = -ENOENT;
>> +		goto e_cpumask;
>> +	}
>> +
>> +	md.u.mon_config = mon_config & 0xFF;
> Same question as previous patch. I do not see this internal
> value used in the code, is storing it necessary?

Storing is not necessary.  As I commented before we need mon_config  as
part of mon_data_bits structure because, it need to be passed to
mon_event_config_read and rdtgroup_mondata_config_write.

In these functions we need evtid and also config value (mon_config).

>
>> +
>> +	/* Pick all the CPUs in the domain instance */
>> +	for_each_cpu(cpu, &d->cpu_mask)
>> +		cpumask_set_cpu(cpu, cpu_mask);
>> +
>> +	cpu = get_cpu();
>> +	/* Update MSR_IA32_EVT_CFG_BASE MSR on this cpu if it's in cpu_mask */
> Please always use caps for CPU.
Sure
>
>> +	if (cpumask_test_cpu(cpu, cpu_mask))
>> +		mon_event_config_write(&md);
>> +
>> +	/* Update MSR_IA32_EVT_CFG_BASE MSR on all other cpus in cpu_mask */
>> +	smp_call_function_many(cpu_mask, mon_event_config_write, &md, 1);
>> +	put_cpu();
> I do not think we need to propagate this pattern more in the resctrl code.
> How about on_each_cpu_mask()? 
Yea. We can do that. It probably better to replace all the current
smp_call_function_many in resctrl code.
>
>> +
>> +	/*
>> +	 * When an Event Configuration is changed, the bandwidth counters
>> +	 * for all RMIDs and Events will be cleared, and the U-bit for every
>> +	 * RMID will be set on the next read to any BwEvent for every RMID.
>> +	 * Clear the mbm_local and mbm_total counts for all the RMIDs.
>> +	 */
>> +	memset(d->mbm_local, 0, sizeof(struct mbm_state) * r->num_rmid);
>> +	memset(d->mbm_total, 0, sizeof(struct mbm_state) * r->num_rmid);
> Could you please check if this is sufficient? Note how "mon_event_read()"
> is called with "first = true" right after the mon sysfs files are created to
> clear the state _and_ initialize the state to set the "prev" MSRs correctly.

I see that it is set

m->prev_bw_msr = m->prev_msr = tval;

With above code we are setting

m->prev_bw_msr = m->prev_msr = 0;

I cannot think of any problems this could cause. Please let me know if you
see a problem.

Thanks

Babu Moger

>
>
>> +
>> +e_cpumask:
>> +	free_cpumask_var(cpu_mask);
>> +
>> +e_unlock:
>> +	rdtgroup_kn_unlock(of->kn);
>> +	cpus_read_unlock();
>> +
>> +	return ret ?: nbytes;
>> +}
>> +
>>  static const struct kernfs_ops kf_mondata_config_ops = {
>>  	.atomic_write_len       = PAGE_SIZE,
>>  	.seq_show               = rdtgroup_mondata_config_show,
>> +	.write                  = rdtgroup_mondata_config_write,
>>  };
>>  
>>  static bool is_cpu_list(struct kernfs_open_file *of)
>>
>>
> Reinette

-- 
Thanks
Babu Moger