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Message-ID: <MW3PR12MB455310F87A49D51194F1D5EB950C9@MW3PR12MB4553.namprd12.prod.outlook.com>
Date: Wed, 23 Nov 2022 22:44:05 +0000
From: "Moger, Babu" <Babu.Moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
"corbet@....net" <corbet@....net>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>
CC: "fenghua.yu@...el.com" <fenghua.yu@...el.com>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
"paulmck@...nel.org" <paulmck@...nel.org>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
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<pawan.kumar.gupta@...ux.intel.com>,
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Subject: RE: [PATCH v8 10/13] x86/resctrl: Add sysfs interface to write
mbm_total_bytes_config
[AMD Official Use Only - General]
Hi Reinette,
> -----Original Message-----
> From: Reinette Chatre <reinette.chatre@...el.com>
> Sent: Tuesday, November 22, 2022 6:22 PM
> To: Moger, Babu <Babu.Moger@....com>; corbet@....net;
> tglx@...utronix.de; mingo@...hat.com; bp@...en8.de
> Cc: fenghua.yu@...el.com; dave.hansen@...ux.intel.com; x86@...nel.org;
> hpa@...or.com; paulmck@...nel.org; akpm@...ux-foundation.org;
> quic_neeraju@...cinc.com; rdunlap@...radead.org;
> damien.lemoal@...nsource.wdc.com; songmuchun@...edance.com;
> peterz@...radead.org; jpoimboe@...nel.org; pbonzini@...hat.com;
> chang.seok.bae@...el.com; pawan.kumar.gupta@...ux.intel.com;
> jmattson@...gle.com; daniel.sneddon@...ux.intel.com; Das1, Sandipan
> <Sandipan.Das@....com>; tony.luck@...el.com; james.morse@....com;
> linux-doc@...r.kernel.org; linux-kernel@...r.kernel.org;
> bagasdotme@...il.com; eranian@...gle.com
> Subject: Re: [PATCH v8 10/13] x86/resctrl: Add sysfs interface to write
> mbm_total_bytes_config
>
> Hi Babu,
>
> On 11/4/2022 1:01 PM, Babu Moger wrote:
> > The current event configuration for mbm_total_bytes can be changed by
> > the user by writing to the file
> > /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config.
> >
> > The event configuration settings are domain specific and will affect
> > all the CPUs in the domain.
> >
> > 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
> > ====
> ===========================================================
> >
> > For example:
> > To change the mbm_total_bytes to count only reads on domain 0, the
> > bits 0, 1, 4 and 5 needs to be set, which is 110011b (in hex 0x33).
> > Run the command.
> > $echo 0=0x33 > /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config
> >
> > To change the mbm_total_bytes to count all the slow memory reads on
> > domain 1, the bits 4 and 5 needs to be set which is 110000b (in hex 0x30).
> > Run the command.
> > $echo 1=0x30 > /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config
> >
> > Signed-off-by: Babu Moger <babu.moger@....com>
> > ---
> > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 130
> > ++++++++++++++++++++++++++++++++
> > 1 file changed, 129 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > index 18f9588a41cf..0cdccb69386e 100644
> > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > @@ -1505,6 +1505,133 @@ static int mbm_local_bytes_config_show(struct
> kernfs_open_file *of,
> > return 0;
> > }
> >
> > +static void mon_event_config_write(void *info) {
> > + struct mon_config_info *mon_info = info;
> > + u32 index;
> > +
> > + index = mon_event_config_index_get(mon_info->evtid);
> > + if (index >= MAX_CONFIG_EVENTS) {
> > + pr_warn_once("Invalid event id %d\n", mon_info->evtid);
> > + return;
> > + }
> > + wrmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, 0);
> }
> > +
> > +static int mbm_config_write(struct rdt_resource *r, struct rdt_domain *d,
> > + u32 evtid, u32 val)
> > +{
> > + struct mon_config_info mon_info = {0};
> > + int ret = 0;
> > +
> > + rdt_last_cmd_clear();
> > +
>
> Why is this extra clear() needed?
I am not sure why I added that. It does not seem required. I can remove it.
>
> > + /* mon_config cannot be more than the supported set of events */
> > + if (val > MAX_EVT_CONFIG_BITS) {
> > + rdt_last_cmd_puts("Invalid event configuration\n");
> > + return -EINVAL;
> > + }
> > +
> > + /*
> > + * Read the current config value first. If both are same then
> > + * we don't need to write it again.
>
> Please no "we". Maybe just "If both are the same then no need to write it
> again."
Ok.
>
> > + */
> > + mon_info.evtid = evtid;
> > + mondata_config_read(d, &mon_info);
>
> Here I see motivation for doing validity check in mondata_config_read() as
> mentioned in feedback for patch #8. If hardware decides to use the other bits in
> that MSR then the check below would have trouble.
>
> > + if (mon_info.mon_config == val)
> > + goto write_exit;
> > +
>
> Could you please follow the custom in this area? Please see goto usage in the
> rest of the file that you are changing. The label should reflect the action being
> jumped to. In that sense, "write_exit" is not clear. A simple "goto out"
> would be clear and matches usage in rest of file.
Ok. Sure
>
> > + mon_info.mon_config = val;
> > +
> > + /*
> > + * Update MSR_IA32_EVT_CFG_BASE MSRs on all the CPUs in the
> > + * domain. The MSRs offset from MSR MSR_IA32_EVT_CFG_BASE
> > + * are scoped at the domain level. Writing any of these MSRs
> > + * on one CPU is supposed to be observed by all CPUs in the
> > + * domain. However, the hardware team recommends to update
> > + * these MSRs on all the CPUs in the domain.
> > + */
> > + on_each_cpu_mask(&d->cpu_mask, mon_event_config_write,
> &mon_info,
> > +1);
> > +
> > + /*
> > + * When an Event Configuration is changed, the bandwidth counters
> > + * for all RMIDs and Events will be cleared by the hardware. The
> > + * hardware also sets MSR_IA32_QM_CTR.Unavailable (bit 62) for
> > + * every RMID on the next read to any event for every RMID.
> > + * Subsequent reads will have MSR_IA32_QM_CTR.Unavailable (bit 62)
> > + * cleared while it is tracked by the hardware. 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);
> > +
> > +write_exit:
> > + return ret;
> > +}
> > +
> > +static int mon_config_parse(struct rdt_resource *r, char *tok, u32
> > +evtid) {
> > + char *dom_str = NULL, *id_str;
> > + unsigned long dom_id, val;
> > + struct rdt_domain *d;
> > + int ret = 0;
> > +
> > +next:
> > + if (!tok || tok[0] == '\0')
> > + return 0;
> > +
> > + /* Start processing the strings for each domain */
> > + dom_str = strim(strsep(&tok, ";"));
> > + id_str = strsep(&dom_str, "=");
> > +
> > + if (!dom_str || kstrtoul(id_str, 10, &dom_id)) {
> > + rdt_last_cmd_puts("Missing '=' or non-numeric domain id\n");
> > + return -EINVAL;
> > + }
> > +
> > + if (!dom_str || kstrtoul(dom_str, 16, &val)) {
> > + rdt_last_cmd_puts("Missing '=' or non-numeric event
> configuration value\n");
> > + return -EINVAL;
> > + }
>
> There is some duplication above ... both if () statememts check for "!dom_str" -
> is one intended to be "!id_str"?
The first check should be !id_str. Will correct it.
> Could both checks really mean that a "=" may be missing?
The second check failure means, there is a missing event configuration value. Will remove "missing =".
>
> > +
> > + list_for_each_entry(d, &r->domains, list) {
> > + if (d->id == dom_id) {
> > + ret = mbm_config_write(r, d, evtid, val);
> > + if (ret)
> > + return -EINVAL;
> > + goto next;
> > + }
> > + }
> > +
> > + return -EINVAL;
> > +}
> > +
> > +static ssize_t mbm_total_bytes_config_write(struct kernfs_open_file *of,
> > + char *buf, size_t nbytes,
> > + loff_t off)
> > +{
> > + struct rdt_resource *r = of->kn->parent->priv;
> > + int ret;
> > +
> > + /* Valid input requires a trailing newline */
> > + if (nbytes == 0 || buf[nbytes - 1] != '\n')
> > + return -EINVAL;
> > +
> > + cpus_read_lock();
> > + mutex_lock(&rdtgroup_mutex);
> > +
> > + rdt_last_cmd_clear();
> > +
> > + buf[nbytes - 1] = '\0';
> > +
> > + ret = mon_config_parse(r, buf, QOS_L3_MBM_TOTAL_EVENT_ID);
> > +
>
> The naming here does not reflect what is done ... much more than parsing is
> done here.
>
> How about renaming mon_config_parse() to mon_config_write(), and
> renaming mon_config_write() to mon_config_write_domain() ?
Sure. Thanks
Babu
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