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Date: Fri, 26 Aug 2022 13:17:48 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, fenghua.yu@...el.com,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc: eranian@...gle.com, dave.hansen@...ux.intel.com, x86@...nel.org,
hpa@...or.com, corbet@....net, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, bagasdotme@...il.com
Subject: Re: [PATCH v3 09/10] x86/resctrl: Add sysfs interface to write the
event configuration
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@....com>
>> Reviewed-by: Ingo Molnar <mingo@...nel.org>
>> ---
>> 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
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