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bh=GFE4CbYuKSbHE7j7girbWxY1eU8a21s7lIm3aRWsPw0=; b=AmZ/cVD4YEMK7kpZF7mCdZpmTWPbkdWLC3xZerLMUNID/WRYMpwmocWm 5M1gCKis7xgUaGHehcLt9HxFM3jDhhXrYKl+tupvBE5ZvabQD3fTo8vHG 8OeAHPaVFsr7tmVSdoM5O9AJvBhFJ6ExhZrQBQhh20/6bNtCqLk7qdUk9 abcc51Js96XGkXB84uLUFcEY0y3YzUcQxTFwPbAeedLqSrwR6bjZsOaHJ OBSpp970erdEEdbw38Tp4MHLPNd0fNFFdbVmwBV5rJ7fVVOYsOrOdWpc3 4P8W5w9Gfnf40mMwLkgiARbcEMzn+zlW/2HyC1v3JBuW4Y2ZLNnaMApUS g==; X-IronPort-AV: E=McAfee;i="6600,9927,11011"; a="4884841" X-IronPort-AV: E=Sophos;i="6.07,119,1708416000"; d="scan'208";a="4884841" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa111.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Mar 2024 14:42:56 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,119,1708416000"; d="scan'208";a="12280155" Received: from agluck-desk3.sc.intel.com ([172.25.222.105]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Mar 2024 14:42:55 -0700 From: Tony Luck To: Fenghua Yu , Reinette Chatre , Peter Newman , Jonathan Corbet , Shuah Khan , x86@kernel.org Cc: Shaopeng Tan , James Morse , Jamie Iles , Babu Moger , Randy Dunlap , Drew Fustini , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, patches@lists.linux.dev, Tony Luck Subject: [PATCH v16 6/9] x86/resctrl: Introduce snc_nodes_per_l3_cache Date: Tue, 12 Mar 2024 14:42:44 -0700 Message-ID: <20240312214247.91772-7-tony.luck@intel.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240312214247.91772-1-tony.luck@intel.com> References: <20240312214247.91772-1-tony.luck@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Intel Sub-NUMA Cluster (SNC) is a feature that subdivides the CPU cores and memory controllers on a socket into two or more groups. These are presented to the operating system as NUMA nodes. This may enable some workloads to have slightly lower latency to memory as the memory controller(s) in an SNC node are electrically closer to the CPU cores on that SNC node. This cost may be offset by lower bandwidth since the memory accesses for each core can only be interleaved between the memory controllers on the same SNC node. Resctrl monitoring on an Intel system depends upon attaching RMIDs to tasks to track L3 cache occupancy and memory bandwidth. There is an MSR that controls how the RMIDs are shared between SNC nodes. The default mode divides them numerically. E.g. when there are two SNC nodes on a socket the lower number half of the RMIDs are given to the first node, the remainder to the second node. This would be difficult to use with the Linux resctrl interface as specific RMID values assigned to resctrl groups are not visible to users. The other mode divides the RMIDs and renumbers the ones on the second SNC node to start from zero. Even with this renumbering SNC mode requires several changes in resctrl behavior for correct operation. Add a global integer "snc_nodes_per_l3_cache" that shows how many SNC nodes share each L3 cache. When "snc_nodes_per_l3_cache" is "1", SNC mode is either not implemented, or not enabled. Update all places to take appropriate action when SNC mode is enabled: 1) The number of logical RMIDs per L3 cache available for use is the number of physical RMIDs divided by the number of SNC nodes. 2) Likewise the "mon_scale" value must be divided by the number of SNC nodes. 3) The RMID renumbering operates when using the value from the IA32_PQR_ASSOC MSR to count accesses by a task. When reading an RMID counter, adjust from the logical RMID to the physical RMID value for the SNC node that it wishes to read and load the adjusted value into the IA32_QM_EVTSEL MSR. 4) Divide the L3 cache between the SNC nodes. Divide the value reported in the resctrl "size" file by the number of SNC nodes because the effective amount of cache that can be allocated is reduced by that factor. 5) Disable the "-o mba_MBps" mount option in SNC mode because the monitoring is being done per SNC node, while the bandwidth allocation is still done at the L3 cache scope. Trying to use this feedback loop might result in contradictory changes to the throttling level coming from each of the SNC node bandwidth measurements. Signed-off-by: Tony Luck --- arch/x86/kernel/cpu/resctrl/internal.h | 2 ++ arch/x86/kernel/cpu/resctrl/core.c | 6 ++++++ arch/x86/kernel/cpu/resctrl/monitor.c | 16 +++++++++++++--- arch/x86/kernel/cpu/resctrl/rdtgroup.c | 5 +++-- 4 files changed, 24 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h index 41a093feb744..786035eff7fb 100644 --- a/arch/x86/kernel/cpu/resctrl/internal.h +++ b/arch/x86/kernel/cpu/resctrl/internal.h @@ -483,6 +483,8 @@ extern struct rdt_hw_resource rdt_resources_all[]; extern struct rdtgroup rdtgroup_default; extern struct dentry *debugfs_resctrl; +extern unsigned int snc_nodes_per_l3_cache; + enum resctrl_res_level { RDT_RESOURCE_L3, RDT_RESOURCE_L2, diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c index c34ce367c456..cb181796f73b 100644 --- a/arch/x86/kernel/cpu/resctrl/core.c +++ b/arch/x86/kernel/cpu/resctrl/core.c @@ -331,6 +331,12 @@ static u32 delay_bw_map(unsigned long bw, struct rdt_resource *r) return r->default_ctrl; } +/* + * Number of SNC nodes that share each L3 cache. Default is 1 for + * systems that do not support SNC, or have SNC disabled. + */ +unsigned int snc_nodes_per_l3_cache = 1; + static void mba_wrmsr_intel(struct msr_param *m) { struct rdt_hw_ctrl_domain *hw_dom = resctrl_to_arch_ctrl_dom(m->dom); diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c index 08d53ce61d01..87badcec2834 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -186,8 +186,18 @@ static inline struct rmid_entry *__rmid_entry(u32 idx) static int __rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *val) { + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; + int cpu = smp_processor_id(); + int rmid_offset = 0; u64 msr_val; + /* + * When SNC mode is on, need to compute the offset to read the + * physical RMID counter for the node to which this CPU belongs. + */ + if (snc_nodes_per_l3_cache > 1) + rmid_offset = (cpu_to_node(cpu) % snc_nodes_per_l3_cache) * r->num_rmid; + /* * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured * with a valid event code for supported resource type and the bits @@ -196,7 +206,7 @@ static int __rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *val) * IA32_QM_CTR.Error (bit 63) and IA32_QM_CTR.Unavailable (bit 62) * are error bits. */ - wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid); + wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid + rmid_offset); rdmsrl(MSR_IA32_QM_CTR, msr_val); if (msr_val & RMID_VAL_ERROR) @@ -1011,8 +1021,8 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r) int ret; resctrl_rmid_realloc_limit = boot_cpu_data.x86_cache_size * 1024; - hw_res->mon_scale = boot_cpu_data.x86_cache_occ_scale; - r->num_rmid = boot_cpu_data.x86_cache_max_rmid + 1; + hw_res->mon_scale = boot_cpu_data.x86_cache_occ_scale / snc_nodes_per_l3_cache; + r->num_rmid = (boot_cpu_data.x86_cache_max_rmid + 1) / snc_nodes_per_l3_cache; hw_res->mbm_width = MBM_CNTR_WIDTH_BASE; if (mbm_offset > 0 && mbm_offset <= MBM_CNTR_WIDTH_OFFSET_MAX) diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c index cc31ede1a1e7..40e6bb8a8fc8 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -1466,7 +1466,7 @@ unsigned int rdtgroup_cbm_to_size(struct rdt_resource *r, } } - return size; + return size / snc_nodes_per_l3_cache; } /* @@ -2346,7 +2346,8 @@ static bool supports_mba_mbps(void) struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl; return (is_mbm_local_enabled() && - r->alloc_capable && is_mba_linear()); + r->alloc_capable && is_mba_linear() && + snc_nodes_per_l3_cache == 1); } /* -- 2.44.0