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Date: Thu, 26 Oct 2023 13:02:14 -0700
From: Tony Luck <tony.luck@...el.com>
To: Fenghua Yu <fenghua.yu@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Peter Newman <peternewman@...gle.com>,
Jonathan Corbet <corbet@....net>,
Shuah Khan <skhan@...uxfoundation.org>, x86@...nel.org
Cc: Shaopeng Tan <tan.shaopeng@...itsu.com>,
James Morse <james.morse@....com>,
Jamie Iles <quic_jiles@...cinc.com>,
Babu Moger <babu.moger@....com>,
Randy Dunlap <rdunlap@...radead.org>,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
patches@...ts.linux.dev, Tony Luck <tony.luck@...el.com>
Subject: [PATCH v3] x86/resctrl: mba_MBps: Fall back to total b/w if local b/w unavailable
On Intel the various resource director technology (RDT) features are all
orthogonal and independently enumerated. Thus it is possible to have
a system that provides "total" memory bandwidth measurements without
providing "local" bandwidth measurements.
If local bandwidth measurement is not available, do not give up on
providing the "mba_MBps" feedback option completely, make the code fall
back to using total bandwidth.
Signed-off-by: Tony Luck <tony.luck@...el.com>
---
Change since v2:
Babu doesn't like the global variable. So here's a version without it.
Note that my preference is still the v2 version. But as I tell newbies
to Linux "Your job isn't to get YOUR patch upstream. You job is to get
the problem fixed.". So taking my own advice I don't really mind
whether v2 or v3 is applied.
arch/x86/kernel/cpu/resctrl/monitor.c | 43 ++++++++++++++++++--------
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 2 +-
2 files changed, 31 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index f136ac046851..29e86310677d 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -418,6 +418,20 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
return 0;
}
+/*
+ * For legacy compatibility use the local memory bandwidth to drive
+ * the mba_MBps feedback control loop. But on platforms that do not
+ * provide the local event fall back to use the total bandwidth event
+ * instead.
+ */
+static enum resctrl_event_id pick_mba_mbps_event(void)
+{
+ if (is_mbm_local_enabled())
+ return QOS_L3_MBM_LOCAL_EVENT_ID;
+
+ return QOS_L3_MBM_TOTAL_EVENT_ID;
+}
+
/*
* mbm_bw_count() - Update bw count from values previously read by
* __mon_event_count().
@@ -431,9 +445,11 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
*/
static void mbm_bw_count(u32 rmid, struct rmid_read *rr)
{
- struct mbm_state *m = &rr->d->mbm_local[rmid];
+ enum resctrl_event_id mba_mbps_evt_id = pick_mba_mbps_event();
u64 cur_bw, bytes, cur_bytes;
+ struct mbm_state *m;
+ m = get_mbm_state(rr->d, rmid, mba_mbps_evt_id);
cur_bytes = rr->val;
bytes = cur_bytes - m->prev_bw_bytes;
m->prev_bw_bytes = cur_bytes;
@@ -518,6 +534,7 @@ void mon_event_count(void *info)
*/
static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
{
+ enum resctrl_event_id mba_mbps_evt_id = pick_mba_mbps_event();
u32 closid, rmid, cur_msr_val, new_msr_val;
struct mbm_state *pmbm_data, *cmbm_data;
u32 cur_bw, delta_bw, user_bw;
@@ -526,14 +543,14 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
struct list_head *head;
struct rdtgroup *entry;
- if (!is_mbm_local_enabled())
+ if (!is_mbm_enabled())
return;
r_mba = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
closid = rgrp->closid;
rmid = rgrp->mon.rmid;
- pmbm_data = &dom_mbm->mbm_local[rmid];
+ pmbm_data = get_mbm_state(dom_mbm, rmid, mba_mbps_evt_id);
dom_mba = get_domain_from_cpu(smp_processor_id(), r_mba);
if (!dom_mba) {
@@ -553,7 +570,7 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
*/
head = &rgrp->mon.crdtgrp_list;
list_for_each_entry(entry, head, mon.crdtgrp_list) {
- cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
+ cmbm_data = get_mbm_state(dom_mbm, entry->mon.rmid, mba_mbps_evt_id);
cur_bw += cmbm_data->prev_bw;
delta_bw += cmbm_data->delta_bw;
}
@@ -595,7 +612,7 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
*/
pmbm_data->delta_comp = true;
list_for_each_entry(entry, head, mon.crdtgrp_list) {
- cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
+ cmbm_data = get_mbm_state(dom_mbm, entry->mon.rmid, mba_mbps_evt_id);
cmbm_data->delta_comp = true;
}
}
@@ -621,15 +638,15 @@ static void mbm_update(struct rdt_resource *r, struct rdt_domain *d, int rmid)
rr.evtid = QOS_L3_MBM_LOCAL_EVENT_ID;
rr.val = 0;
__mon_event_count(rmid, &rr);
-
- /*
- * Call the MBA software controller only for the
- * control groups and when user has enabled
- * the software controller explicitly.
- */
- if (is_mba_sc(NULL))
- mbm_bw_count(rmid, &rr);
}
+
+ /*
+ * Call the MBA software controller only for the
+ * control groups and when user has enabled
+ * the software controller explicitly.
+ */
+ if (is_mba_sc(NULL))
+ mbm_bw_count(rmid, &rr);
}
/*
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 69a1de92384a..0c4f8a1b8df0 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2294,7 +2294,7 @@ static bool supports_mba_mbps(void)
{
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
- return (is_mbm_local_enabled() &&
+ return (is_mbm_enabled() &&
r->alloc_capable && is_mba_linear());
}
--
2.41.0
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