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 <[email protected]> Reviewed-by: Tony Luck <[email protected]> --- 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
