From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CA929384CD7 for ; Wed, 13 May 2026 20:33:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778704418; cv=none; b=XS4hFIWAtoKlvfHUg5ngzaDvgGMPuRPhvTziFxsKy3CSSaRAm2RGEbumT85oKEx+GloK3ZC01NdakQJNmLa0UQ4ZwshbJDGJPYewwv0Uih9gvVX+FDk/1bfkRff/1qWZzbG7gXOWNo/Iq5+cS3nle02nEdXxOT0YFa8965dR2+c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778704418; c=relaxed/simple; bh=E0nEgU8NHJbSvpI+37J42hPBxHwU7Sw0zA2+0Rlp2Nw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Ra0mAU5b1O7GlfQ4DjOi2pRS60BJn9T2NDJePcraX9CAVb2I+owMqUS1fzNtT/6KIx6bmFKPY04OiROLFs4ptWq4/aHe4H6eKs3YzKVDEPBThG/yzQmSbNlfHlkU3YGt/GxfoBf4FUCHgUVcoyR+CzeRRLgwwClyMKcGDUeLNmg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=hAsd8azL; arc=none smtp.client-ip=198.175.65.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="hAsd8azL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1778704417; x=1810240417; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=E0nEgU8NHJbSvpI+37J42hPBxHwU7Sw0zA2+0Rlp2Nw=; b=hAsd8azLyLnLG/XbuZB8UKl5HyYm4bFgjsvG3q3AXaoSEQp6OWl5B7E7 d9k4lEQFVfnl3mX4YO05lVmgutwlHbSE8dL4kgxB0oR+gFgnH9APGwHzi oNXic/z9WdRfq17a+gPWZZ6EEVkNh77MhsGGnSf/HD8rjtTN1o5EV+d9G GGRrVM2tleg7BjNcwiUSsxsNQYCqExVuqEjNm/Xx6Irpd0wMSipNp/JSX v5NDZhVzpQFP3GFOXu4ZepFlodeKOgZTg6fMrQ1FbLvj0q3rJmjRUKshe g2Sa1K/pzg7zSQ766mht2q4E3DWuNeNxxXud9VHkpcADPc1Wj/lsdWpvG w==; X-CSE-ConnectionGUID: kzBcBWY3TS6x7e3cKIeOxQ== X-CSE-MsgGUID: H4endoy3SCK3DsW6x+jYTw== X-IronPort-AV: E=McAfee;i="6800,10657,11785"; a="79623037" X-IronPort-AV: E=Sophos;i="6.23,233,1770624000"; d="scan'208";a="79623037" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 May 2026 13:33:36 -0700 X-CSE-ConnectionGUID: b3WkzRXdTkiqPyZP/HGnog== X-CSE-MsgGUID: rRXopY6dTjKDQkwp+cNsNg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,233,1770624000"; d="scan'208";a="238076338" Received: from b04f130c83f2.jf.intel.com ([10.165.154.98]) by orviesa008.jf.intel.com with ESMTP; 13 May 2026 13:33:35 -0700 From: Tim Chen To: Peter Zijlstra , Ingo Molnar , K Prateek Nayak , Vincent Guittot Cc: Chen Yu , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Madadi Vineeth Reddy , Hillf Danton , Shrikanth Hegde , Jianyong Wu , Yangyu Chen , Tingyin Duan , Vern Hao , Vern Hao , Len Brown , Tim Chen , Aubrey Li , Zhao Liu , Chen Yu , Adam Li , Aaron Lu , Tim Chen , Josh Don , Gavin Guo , Qais Yousef , Libo Chen , Luo Gengkun , linux-kernel@vger.kernel.org Subject: [Patch v4 04/16] sched/cache: Calculate the LLC size and store it in sched_domain Date: Wed, 13 May 2026 13:39:15 -0700 Message-Id: <37afee09ff608034da0ce149e72d33b6f4698edf.1778703694.git.tim.c.chen@linux.intel.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chen Yu Cache aware scheduling needs to know the LLC size that a process can use, so as to avoid memory-intensive tasks from being over-aggregated on a single LLC. Introduce a preparation patch to add get_effective_llc_bytes() to get the LLC size that a CPU can use. The function can be further enhanced by subtracting the LLC cache ways reserved by resctrl (CAT in Intel RDT, etc). Tested-by: Tingyin Duan Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Chen Yu Co-developed-by: Tim Chen Signed-off-by: Tim Chen --- drivers/base/cacheinfo.c | 23 ++++++++ include/linux/cacheinfo.h | 1 + include/linux/sched/topology.h | 7 +++ kernel/sched/topology.c | 98 ++++++++++++++++++++++++++++++++-- 4 files changed, 126 insertions(+), 3 deletions(-) diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c index 391ac5e3d2f5..70701d3bc81c 100644 --- a/drivers/base/cacheinfo.c +++ b/drivers/base/cacheinfo.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include #include @@ -68,6 +69,24 @@ bool last_level_cache_is_valid(unsigned int cpu) } +/* + * Get the cacheinfo of the LLC associated with @cpu. + * Derived from update_per_cpu_data_slice_size_cpu(). + */ +struct cacheinfo *get_cpu_cacheinfo_llc(unsigned int cpu) +{ + struct cacheinfo *llc; + + if (!last_level_cache_is_valid(cpu)) + return NULL; + + llc = per_cpu_cacheinfo_idx(cpu, cache_leaves(cpu) - 1); + if (llc->type != CACHE_TYPE_DATA && llc->type != CACHE_TYPE_UNIFIED) + return NULL; + + return llc; +} + bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y) { struct cacheinfo *llc_x, *llc_y; @@ -1018,6 +1037,7 @@ static int cacheinfo_cpu_online(unsigned int cpu) goto err; if (cpu_map_shared_cache(true, cpu, &cpu_map)) update_per_cpu_data_slice_size(true, cpu, cpu_map); + sched_update_llc_bytes(cpu); return 0; err: free_cache_attributes(cpu); @@ -1036,6 +1056,9 @@ static int cacheinfo_cpu_pre_down(unsigned int cpu) free_cache_attributes(cpu); if (nr_shared > 1) update_per_cpu_data_slice_size(false, cpu, cpu_map); + + sched_update_llc_bytes(cpu); + return 0; } diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h index c8f4f0a0b874..fc879ac4cc4f 100644 --- a/include/linux/cacheinfo.h +++ b/include/linux/cacheinfo.h @@ -89,6 +89,7 @@ int populate_cache_leaves(unsigned int cpu); int cache_setup_acpi(unsigned int cpu); bool last_level_cache_is_valid(unsigned int cpu); bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y); +struct cacheinfo *get_cpu_cacheinfo_llc(unsigned int cpu); int fetch_cache_info(unsigned int cpu); int detect_cache_attributes(unsigned int cpu); #ifndef CONFIG_ACPI_PPTT diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index 0036d6b4bd67..fe09d3268bc9 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -106,6 +106,7 @@ struct sched_domain { #ifdef CONFIG_SCHED_CACHE unsigned int llc_max; unsigned int *llc_counts __counted_by_ptr(llc_max); + unsigned long llc_bytes; #endif #ifdef CONFIG_SCHEDSTATS @@ -265,4 +266,10 @@ static inline int task_node(const struct task_struct *p) return cpu_to_node(task_cpu(p)); } +#ifdef CONFIG_SCHED_CACHE +extern void sched_update_llc_bytes(unsigned int cpu); +#else +static inline void sched_update_llc_bytes(unsigned int cpu) { } +#endif + #endif /* _LINUX_SCHED_TOPOLOGY_H */ diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 9fc99346ef4f..7248a7279abe 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -776,9 +776,11 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu) /* move buffer to parent as child is being destroyed */ sd->llc_counts = tmp->llc_counts; sd->llc_max = tmp->llc_max; + sd->llc_bytes = tmp->llc_bytes; /* make sure destroy_sched_domain() does not free it */ tmp->llc_counts = NULL; tmp->llc_max = 0; + tmp->llc_bytes = 0; #endif /* * sched groups hold the flags of the child sched @@ -831,10 +833,42 @@ DEFINE_STATIC_KEY_FALSE(sched_cache_active); /* user wants cache aware scheduling [0 or 1] */ int sysctl_sched_cache_user = 1; +/* + * Get the effective LLC size in bytes that @cpu's bottom sched_domain + * can use. A CPU within a cpuset partition can only use a proportion + * of the physical LLC, scaled by the ratio of the partition's span + * weight to the hardware LLC sharing weight. @sd should be the + * topmost domain with SD_SHARE_LLC. + * + * Returns 0 if cacheinfo is not yet populated. This happens during + * early boot when build_sched_domains() runs before the generic + * cacheinfo framework has been initialized (cacheinfo_cpu_online() + * is a device_initcall cpuhp callback). In that case, + * cacheinfo_cpu_online() will later call sched_update_llc_bytes() + * to fill in the bottom domain's llc_bytes once the cache attributes + * are available. + */ +static unsigned long get_effective_llc_bytes(int cpu, + struct sched_domain *sd) +{ + struct cacheinfo *ci; + unsigned int hw_weight; + + ci = get_cpu_cacheinfo_llc(cpu); + if (!ci) + return 0; + + hw_weight = cpumask_weight(&ci->shared_cpu_map); + if (!hw_weight) + return 0; + + return div_u64((u64)ci->size * sd->span_weight, hw_weight); +} + static bool alloc_sd_llc(const struct cpumask *cpu_map, struct s_data *d) { - struct sched_domain *sd; + struct sched_domain *sd, *top_llc, *parent; unsigned int *p; int i; @@ -848,8 +882,24 @@ static bool alloc_sd_llc(const struct cpumask *cpu_map, if (!p) goto err; - sd->llc_max = max_lid + 1; - sd->llc_counts = p; + top_llc = sd; + /* + * Find the topmost SD_SHARE_LLC domain. + * Not yet attached to the CPU, so per_cpu(sd_llc, i) + * can not be used. + */ + while ((parent = rcu_dereference_protected(top_llc->parent, true)) && + (parent->flags & SD_SHARE_LLC)) + top_llc = parent; + + if (top_llc->flags & SD_SHARE_LLC) { + sd->llc_max = max_lid + 1; + sd->llc_counts = p; + sd->llc_bytes = get_effective_llc_bytes(i, top_llc); + } else { + /* avoid memory leak */ + kfree(p); + } } return true; @@ -860,6 +910,7 @@ static bool alloc_sd_llc(const struct cpumask *cpu_map, kfree(sd->llc_counts); sd->llc_counts = NULL; sd->llc_max = 0; + sd->llc_bytes = 0; } } @@ -919,6 +970,47 @@ void sched_cache_active_set_unlocked(void) { return sched_cache_active_set(false); } + +/* + * Update the bottom sched_domain's llc_bytes for @cpu and all its + * LLC siblings. Called from cacheinfo_cpu_online() or + * cacheinfo_cpu_pre_down() with cpu hotplug lock held. + * + * Note: get_effective_llc_bytes() returns 0 on PowerPC. + * thus cache aware scheduling is disabled on PowerPC for + * now. PowerPC does not use the generic cacheinfo framework -- + * it has its own cacheinfo with a separate struct cache hierarchy + * and does not populates the per-CPU struct cpu_cacheinfo array + * that get_cpu_cacheinfo_llc() reads. + */ +void sched_update_llc_bytes(unsigned int cpu) +{ + struct sched_domain *sd, *sdp; + unsigned int i; + + sched_domains_mutex_lock(); + + sdp = rcu_dereference_sched_domain(per_cpu(sd_llc, cpu)); + if (!sdp) + goto unlock; + + /* + * ci->shared_cpu_map is built incrementally as CPUs come + * online, so the first CPU in an LLC initially sees + * hw_weight == 1 and computes an inflated llc_bytes in + * get_effective_llc_bytes(). Re-evaluating every LLC + * sibling on each online event corrects this once the full + * shared_cpu_map is known. + */ + for_each_cpu(i, sched_domain_span(sdp)) { + sd = rcu_dereference_sched_domain(cpu_rq(i)->sd); + if (sd) + sd->llc_bytes = get_effective_llc_bytes(i, sdp); + } + +unlock: + sched_domains_mutex_unlock(); +} #else static bool alloc_sd_llc(const struct cpumask *cpu_map, struct s_data *d) -- 2.32.0