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Use a large kmem arena import size on NUMA systems.

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This helps minimize internal fragmentation that occurs when 2MB imports
are interleaved across NUMA domains.  Virtually all KVA allocations on
direct map platforms consume more than one page, so the fragmentation
manifests as runs of 511 4KB page mappings in the kernel.

Reviewed by:	alc, kib
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D26050
This commit is contained in:
Mark Johnston 2020-08-26 14:31:48 +00:00
parent 41c6838786
commit aea9103e06
1 changed files with 16 additions and 2 deletions
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18
sys/vm/vm_kern.c
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@ -128,6 +128,7 @@ SYSCTL_ULONG(_vm, OID_AUTO, max_kernel_address, CTLFLAG_RD,
#define KVA_QUANTUM_SHIFT (8 + PAGE_SHIFT)
#endif
#define KVA_QUANTUM (1 << KVA_QUANTUM_SHIFT)
#define KVA_NUMA_IMPORT_QUANTUM (KVA_QUANTUM * 128)
extern void uma_startup2(void);
@ -745,6 +746,7 @@ kva_import_domain(void *arena, vmem_size_t size, int flags, vmem_addr_t *addrp)
void
kmem_init(vm_offset_t start, vm_offset_t end)
{
vm_size_t quantum;
int domain;
vm_map_init(kernel_map, kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
@ -773,11 +775,21 @@ kmem_init(vm_offset_t start, vm_offset_t end)
#endif
vm_map_unlock(kernel_map);
/*
* Use a large import quantum on NUMA systems. This helps minimize
* interleaving of superpages, reducing internal fragmentation within
* the per-domain arenas.
*/
if (vm_ndomains > 1 && PMAP_HAS_DMAP)
quantum = KVA_NUMA_IMPORT_QUANTUM;
else
quantum = KVA_QUANTUM;
/*
* Initialize the kernel_arena. This can grow on demand.
*/
vmem_init(kernel_arena, "kernel arena", 0, 0, PAGE_SIZE, 0, 0);
vmem_set_import(kernel_arena, kva_import, NULL, NULL, KVA_QUANTUM);
vmem_set_import(kernel_arena, kva_import, NULL, NULL, quantum);
for (domain = 0; domain < vm_ndomains; domain++) {
/*
@ -789,13 +801,15 @@ kmem_init(vm_offset_t start, vm_offset_t end)
vm_dom[domain].vmd_kernel_arena = vmem_create(
"kernel arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
vmem_set_import(vm_dom[domain].vmd_kernel_arena,
kva_import_domain, NULL, kernel_arena, KVA_QUANTUM);
kva_import_domain, NULL, kernel_arena, quantum);
/*
* In architectures with superpages, maintain separate arenas
* for allocations with permissions that differ from the
* "standard" read/write permissions used for kernel memory,
* so as not to inhibit superpage promotion.
*
* Use the base import quantum since this arena is rarely used.
*/
#if VM_NRESERVLEVEL > 0
vm_dom[domain].vmd_kernel_rwx_arena = vmem_create(