From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- arch/arc/mm/init.c | 178 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 178 insertions(+) create mode 100644 arch/arc/mm/init.c (limited to 'arch/arc/mm/init.c') diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c new file mode 100644 index 000000000..d6b5c27a0 --- /dev/null +++ b/arch/arc/mm/init.c @@ -0,0 +1,178 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) + */ + +#include +#include +#include +#ifdef CONFIG_BLK_DEV_INITRD +#include +#endif +#include +#include +#include +#include +#include +#include +#include +#include + +pgd_t swapper_pg_dir[PTRS_PER_PGD] __aligned(PAGE_SIZE); + +static const unsigned long low_mem_start = CONFIG_LINUX_RAM_BASE; +static unsigned long low_mem_sz; + +#ifdef CONFIG_HIGHMEM +static unsigned long min_high_pfn, max_high_pfn; +static phys_addr_t high_mem_start; +static phys_addr_t high_mem_sz; +unsigned long arch_pfn_offset; +EXPORT_SYMBOL(arch_pfn_offset); +#endif + +long __init arc_get_mem_sz(void) +{ + return low_mem_sz; +} + +/* User can over-ride above with "mem=nnn[KkMm]" in cmdline */ +static int __init setup_mem_sz(char *str) +{ + low_mem_sz = memparse(str, NULL) & PAGE_MASK; + + /* early console might not be setup yet - it will show up later */ + pr_info("\"mem=%s\": mem sz set to %ldM\n", str, TO_MB(low_mem_sz)); + + return 0; +} +early_param("mem", setup_mem_sz); + +void __init early_init_dt_add_memory_arch(u64 base, u64 size) +{ + int in_use = 0; + + if (!low_mem_sz) { + if (base != low_mem_start) + panic("CONFIG_LINUX_RAM_BASE != DT memory { }"); + + low_mem_sz = size; + in_use = 1; + memblock_add_node(base, size, 0, MEMBLOCK_NONE); + } else { +#ifdef CONFIG_HIGHMEM + high_mem_start = base; + high_mem_sz = size; + in_use = 1; + memblock_add_node(base, size, 1, MEMBLOCK_NONE); + memblock_reserve(base, size); +#endif + } + + pr_info("Memory @ %llx [%lldM] %s\n", + base, TO_MB(size), !in_use ? "Not used":""); +} + +void __init arch_zone_limits_init(unsigned long *max_zone_pfn) +{ + /*----------------- node/zones setup --------------------------*/ + max_zone_pfn[ZONE_NORMAL] = max_low_pfn; + +#ifdef CONFIG_HIGHMEM + /* + * max_high_pfn should be ok here for both HIGHMEM and HIGHMEM+PAE. + * For HIGHMEM without PAE max_high_pfn should be less than + * min_low_pfn to guarantee that these two regions don't overlap. + * For PAE case highmem is greater than lowmem, so it is natural + * to use max_high_pfn. + * + * In both cases, holes should be handled by pfn_valid(). + */ + max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; +#endif +} + +/* + * First memory setup routine called from setup_arch() + * 1. setup swapper's mm @init_mm + * 2. Count the pages we have and setup bootmem allocator + * 3. zone setup + */ +void __init setup_arch_memory(void) +{ + setup_initial_init_mm(_text, _etext, _edata, _end); + + /* first page of system - kernel .vector starts here */ + min_low_pfn = virt_to_pfn((void *)CONFIG_LINUX_RAM_BASE); + + /* Last usable page of low mem */ + max_low_pfn = max_pfn = PFN_DOWN(low_mem_start + low_mem_sz); + + /*------------- bootmem allocator setup -----------------------*/ + + /* + * seed the bootmem allocator after any DT memory node parsing or + * "mem=xxx" cmdline overrides have potentially updated @arc_mem_sz + * + * Only low mem is added, otherwise we have crashes when allocating + * mem_map[] itself. NO_BOOTMEM allocates mem_map[] at the end of + * avail memory, ending in highmem with a > 32-bit address. However + * it then tries to memset it with a truncaed 32-bit handle, causing + * the crash + */ + + memblock_reserve(CONFIG_LINUX_LINK_BASE, + __pa(_end) - CONFIG_LINUX_LINK_BASE); + +#ifdef CONFIG_BLK_DEV_INITRD + if (phys_initrd_size) { + memblock_reserve(phys_initrd_start, phys_initrd_size); + initrd_start = (unsigned long)__va(phys_initrd_start); + initrd_end = initrd_start + phys_initrd_size; + } +#endif + + early_init_fdt_reserve_self(); + early_init_fdt_scan_reserved_mem(); + + memblock_dump_all(); + +#ifdef CONFIG_HIGHMEM + /* + * On ARC (w/o PAE) HIGHMEM addresses are actually smaller (0 based) + * than addresses in normal aka low memory (0x8000_0000 based). + * Even with PAE, the huge peripheral space hole would waste a lot of + * mem with single contiguous mem_map[]. + * Thus when HIGHMEM on ARC is enabled the memory map corresponding + * to the hole is freed and ARC specific version of pfn_valid() + * handles the hole in the memory map. + */ + + min_high_pfn = PFN_DOWN(high_mem_start); + max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz); + + arch_pfn_offset = min(min_low_pfn, min_high_pfn); + kmap_init(); +#endif /* CONFIG_HIGHMEM */ +} + +void __init arch_mm_preinit(void) +{ +#ifdef CONFIG_HIGHMEM + memblock_phys_free(high_mem_start, high_mem_sz); +#endif + + BUILD_BUG_ON((PTRS_PER_PGD * sizeof(pgd_t)) > PAGE_SIZE); + BUILD_BUG_ON((PTRS_PER_PUD * sizeof(pud_t)) > PAGE_SIZE); + BUILD_BUG_ON((PTRS_PER_PMD * sizeof(pmd_t)) > PAGE_SIZE); + BUILD_BUG_ON((PTRS_PER_PTE * sizeof(pte_t)) > PAGE_SIZE); +} + +#ifdef CONFIG_HIGHMEM +int pfn_valid(unsigned long pfn) +{ + return (pfn >= min_high_pfn && pfn <= max_high_pfn) || + (pfn >= min_low_pfn && pfn <= max_low_pfn); +} +EXPORT_SYMBOL(pfn_valid); +#endif -- cgit v1.3.1