[PATCH] x86/resctrl: Correct MBM total and local values
From: Fenghua Yu
Date: Mon Sep 28 2020 - 19:16:35 EST
MBM total and local readings are corrected by the following correction
factor table on Broadwell server and Skylake server.
core rmid rmid correction
count count threshold factor
1 8 0 1.000000
2 16 0 1.000000
3 24 15 0.969650
4 32 0 1.000000
5 40 31 1.066667
6 48 31 0.969650
7 56 47 1.142857
8 64 0 1.000000
9 72 63 1.185115
10 80 63 1.066553
11 88 79 1.454545
12 96 0 1.000000
13 104 95 1.230769
14 112 95 1.142857
15 120 95 1.066667
16 128 0 1.000000
17 136 127 1.254863
18 144 127 1.185255
19 152 0 1.000000
20 160 127 1.066667
21 168 0 1.000000
22 176 159 1.454334
23 184 0 1.000000
24 192 127 0.969744
25 200 191 1.280246
26 208 191 1.230921
27 216 0 1.000000
28 224 191 1.143118
If rmid > rmid threshold, MBM total and local values should be multipled
by the correction factor.
The above table is modified for better code:
1. The threshold 0 is changed to rmid count - 1 so we don't do correction
for the case.
2. Correction factor is normalized to 2^20 for better performance
by avoiding floating point and division calculation in corrected
MBM values.
Detailed information about the correction is described in erratum SKX99:
https://www.intel.com/content/www/us/en/processors/xeon/scalable/xeon-scalable-spec-update.html
and BDF102: https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-v4-spec-update.pdf
The problem is described in details in "3.6 Intel MBM RMID Imbalance":
https://software.intel.com/content/www/us/en/develop/articles/intel-resource-director-technology-rdt-reference-manual.html
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
Applied to tip:x86/cache.
arch/x86/kernel/cpu/resctrl/core.c | 4 ++
arch/x86/kernel/cpu/resctrl/internal.h | 1 +
arch/x86/kernel/cpu/resctrl/monitor.c | 75 +++++++++++++++++++++++++-
3 files changed, 78 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 9e1712e8aef7..efe3ed61ae0c 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -893,6 +893,10 @@ static __init void __check_quirks_intel(void)
set_rdt_options("!cmt,!mbmtotal,!mbmlocal,!l3cat");
else
set_rdt_options("!l3cat");
+ /* FALLTHROUGH */
+ case INTEL_FAM6_BROADWELL_X:
+ intel_rdt_mbm_quirk();
+ break;
}
}
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 80fa997fae60..0be0232ac03a 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -616,6 +616,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
void mbm_setup_overflow_handler(struct rdt_domain *dom,
unsigned long delay_ms);
void mbm_handle_overflow(struct work_struct *work);
+void intel_rdt_mbm_quirk(void);
bool is_mba_sc(struct rdt_resource *r);
void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm);
u32 delay_bw_map(unsigned long bw, struct rdt_resource *r);
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 54dffe574e67..05e06744e4b1 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -18,6 +18,7 @@
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/cpu_device_id.h>
+#include <asm/intel-family.h>
#include "internal.h"
struct rmid_entry {
@@ -64,6 +65,61 @@ unsigned int rdt_mon_features;
*/
unsigned int resctrl_cqm_threshold;
+#define CF(cf) ((unsigned long)(1048576 * (cf) + 0.5))
+
+/*
+ * MBM total and local correction table indexed by CBO which is equal to
+ * (x86_cache_max_rmid + 1) / 8 - 1 and is from 0 up to 27.
+ * The correction factor is normalized to 2^20 (1048576) so it's faster
+ * to calculate corrected value by shifting:
+ * corrected_value = (original_value * correction_factor) >> 20
+ */
+static struct mbm_creation_factor_table {
+ u32 rmidthreshold;
+ u64 cf;
+} mbm_cf_table[] = {
+ {7, CF(1.000000)},
+ {15, CF(1.000000)},
+ {15, CF(0.969650)},
+ {31, CF(1.000000)},
+ {31, CF(1.066667)},
+ {31, CF(0.969650)},
+ {47, CF(1.142857)},
+ {63, CF(1.000000)},
+ {63, CF(1.185115)},
+ {63, CF(1.066553)},
+ {79, CF(1.454545)},
+ {95, CF(1.000000)},
+ {95, CF(1.230769)},
+ {95, CF(1.142857)},
+ {95, CF(1.066667)},
+ {127, CF(1.000000)},
+ {127, CF(1.254863)},
+ {127, CF(1.185255)},
+ {151, CF(1.000000)},
+ {127, CF(1.066667)},
+ {167, CF(1.000000)},
+ {159, CF(1.454334)},
+ {183, CF(1.000000)},
+ {127, CF(0.969744)},
+ {191, CF(1.280246)},
+ {191, CF(1.230921)},
+ {215, CF(1.000000)},
+ {191, CF(1.143118)},
+};
+
+static u32 mbm_cf_rmidthreshold = UINT_MAX;
+static u64 mbm_cf;
+
+static inline u64 corrected_mbm_count(u32 rmid, unsigned long val)
+{
+ /* Correct MBM value. */
+ if (rmid > mbm_cf_rmidthreshold)
+ val = (val * mbm_cf) >> 20;
+
+ return val;
+}
+
static inline struct rmid_entry *__rmid_entry(u32 rmid)
{
struct rmid_entry *entry;
@@ -260,7 +316,8 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
m->chunks += chunks;
m->prev_msr = tval;
- rr->val += m->chunks;
+ rr->val += corrected_mbm_count(rmid, m->chunks);
+
return 0;
}
@@ -280,7 +337,7 @@ static void mbm_bw_count(u32 rmid, struct rmid_read *rr)
chunks = mbm_overflow_count(m->prev_bw_msr, tval, rr->r->mbm_width);
m->chunks += chunks;
- cur_bw = (chunks * r->mon_scale) >> 20;
+ cur_bw = (corrected_mbm_count(rmid, chunks) * r->mon_scale) >> 20;
if (m->delta_comp)
m->delta_bw = abs(cur_bw - m->prev_bw);
@@ -644,3 +701,17 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
return 0;
}
+
+void intel_rdt_mbm_quirk(void)
+{
+ int cf_index;
+
+ cf_index = (boot_cpu_data.x86_cache_max_rmid + 1) / 8 - 1;
+ if (cf_index >= ARRAY_SIZE(mbm_cf_table)) {
+ pr_info("No MBM correction factor available\n");
+ return;
+ }
+
+ mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;
+ mbm_cf = mbm_cf_table[cf_index].cf;
+}
--
2.28.0