[PATCH v4] arm64: mm: fix linear mem mapping access performance degradation
Guanghui Feng
guanghuifeng at linux.alibaba.com
Sat Jul 2 08:57:53 PDT 2022
The arm64 can build 2M/1G block/sectiion mapping. When using DMA/DMA32 zone
(enable crashkernel, disable rodata full, disable kfence), the mem_map will
use non block/section mapping(for crashkernel requires to shrink the region
in page granularity). But it will degrade performance when doing larging
continuous mem access in kernel(memcpy/memmove, etc).
There are many changes and discussions:
commit 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
platforms with no DMA memory zones")
commit 0a30c53573b0 ("arm64: mm: Move reserve_crashkernel() into
mem_init()")
commit 2687275a5843 ("arm64: Force NO_BLOCK_MAPPINGS if crashkernel
reservation is required")
This patch changes mem_map to use block/section mapping with crashkernel.
Firstly, do block/section mapping(normally 2M or 1G) for all avail mem at
mem_map, reserve crashkernel memory. And then walking pagetable to split
block/section mapping to non block/section mapping(normally 4K) [[[only]]]
for crashkernel mem. So the linear mem mapping use block/section mapping
as more as possible. We will reduce the cpu dTLB miss conspicuously, and
accelerate mem access about 10-20% performance improvement.
I have tested it with pft(Page Fault Test) and fio, obtained great
performace improvement.
For fio test:
1.prepare ramdisk
modprobe -r brd
modprobe brd rd_nr=1 rd_size=67108864
dmsetup remove_all
wipefs -a --force /dev/ram0
mkfs -t ext4 -E lazy_itable_init=0,lazy_journal_init=0 -q -F /dev/ram0
mkdir -p /fs/ram0
mount -t ext4 /dev/ram0 /fs/ram0
2.prepare fio paremeter in x.fio file:
[global]
bs=4k
ioengine=psync
iodepth=128
size=32G
direct=1
invalidate=1
group_reporting
thread=1
rw=read
directory=/fs/ram0
numjobs=1
[task_0]
cpus_allowed=16
stonewall=1
3.run testcase:
perf stat -e dTLB-load-misses fio x.fio
4.contrast
------------------------
without patch with patch
fio READ aggrb=1493.2MB/s aggrb=1775.3MB/s
dTLB-load-misses 1,818,320,693 438,729,774
time elapsed(s) 70.500326434 62.877316408
user(s) 15.926332000 15.684721000
sys(s) 54.211939000 47.046165000
5.conclusion
Using this patch will reduce dTLB misses and improve performace greatly.
Signed-off-by: Guanghui Feng <guanghuifeng at linux.alibaba.com>
---
arch/arm64/include/asm/mmu.h | 1 +
arch/arm64/mm/init.c | 8 +-
arch/arm64/mm/mmu.c | 176 +++++++++++++++++++++++++++++++------------
3 files changed, 132 insertions(+), 53 deletions(-)
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 48f8466..1a46b81 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -63,6 +63,7 @@ static inline bool arm64_kernel_unmapped_at_el0(void)
extern void arm64_memblock_init(void);
extern void paging_init(void);
extern void bootmem_init(void);
+extern void map_crashkernel(void);
extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
extern void init_mem_pgprot(void);
extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 339ee84..241d27e 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -190,6 +190,7 @@ static void __init reserve_crashkernel(void)
crashk_res.start = crash_base;
crashk_res.end = crash_base + crash_size - 1;
insert_resource(&iomem_resource, &crashk_res);
+ map_crashkernel();
}
/*
@@ -388,10 +389,6 @@ void __init arm64_memblock_init(void)
}
early_init_fdt_scan_reserved_mem();
-
- if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
- reserve_crashkernel();
-
high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
}
@@ -438,8 +435,7 @@ void __init bootmem_init(void)
* request_standard_resources() depends on crashkernel's memory being
* reserved, so do it here.
*/
- if (IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32))
- reserve_crashkernel();
+ reserve_crashkernel();
memblock_dump_all();
}
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 626ec32..76a4ff0 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -65,6 +65,10 @@
static DEFINE_SPINLOCK(swapper_pgdir_lock);
static DEFINE_MUTEX(fixmap_lock);
+static void unmap_hotplug_range(unsigned long addr, unsigned long end,
+ bool free_mapped, struct vmem_altmap *altmap,
+ pgprot_t prot,
+ phys_addr_t (*pgtable_alloc)(int), int flags);
void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd)
{
@@ -483,20 +487,49 @@ void __init mark_linear_text_alias_ro(void)
PAGE_KERNEL_RO);
}
-static bool crash_mem_map __initdata;
+#ifdef CONFIG_KEXEC_CORE
+static phys_addr_t __init early_crashkernel_pgtable_alloc(int shift)
+{
+ phys_addr_t phys;
+ void *ptr;
+
+ phys = memblock_phys_alloc_range(PAGE_SIZE, PAGE_SIZE, 0,
+ MEMBLOCK_ALLOC_NOLEAKTRACE);
+ if (!phys)
+ panic("Failed to allocate page table page\n");
+
+ ptr = (void *)__phys_to_virt(phys);
+ memset(ptr, 0, PAGE_SIZE);
+ return phys;
+}
-static int __init enable_crash_mem_map(char *arg)
+void __init map_crashkernel(void)
{
- /*
- * Proper parameter parsing is done by reserve_crashkernel(). We only
- * need to know if the linear map has to avoid block mappings so that
- * the crashkernel reservations can be unmapped later.
- */
- crash_mem_map = true;
+ phys_addr_t start, end, size;
- return 0;
+ if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE))
+ return;
+
+ if (!crashk_res.end)
+ return;
+
+ start = crashk_res.start & PAGE_MASK;
+ end = PAGE_ALIGN(crashk_res.end);
+ size = end - start;
+
+ unmap_hotplug_range(__phys_to_virt(start), __phys_to_virt(end), false,
+ NULL, PAGE_KERNEL, early_crashkernel_pgtable_alloc,
+ NO_EXEC_MAPPINGS);
+ __create_pgd_mapping(swapper_pg_dir, crashk_res.start,
+ __phys_to_virt(crashk_res.start),
+ size, PAGE_KERNEL,
+ early_crashkernel_pgtable_alloc,
+ NO_EXEC_MAPPINGS | NO_BLOCK_MAPPINGS |
+ NO_CONT_MAPPINGS);
}
-early_param("crashkernel", enable_crash_mem_map);
+#else
+void __init mapping_crashkernel(void) {}
+#endif
static void __init map_mem(pgd_t *pgdp)
{
@@ -527,17 +560,6 @@ static void __init map_mem(pgd_t *pgdp)
*/
memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
-#ifdef CONFIG_KEXEC_CORE
- if (crash_mem_map) {
- if (IS_ENABLED(CONFIG_ZONE_DMA) ||
- IS_ENABLED(CONFIG_ZONE_DMA32))
- flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
- else if (crashk_res.end)
- memblock_mark_nomap(crashk_res.start,
- resource_size(&crashk_res));
- }
-#endif
-
/* map all the memory banks */
for_each_mem_range(i, &start, &end) {
if (start >= end)
@@ -570,19 +592,6 @@ static void __init map_mem(pgd_t *pgdp)
* in page granularity and put back unused memory to buddy system
* through /sys/kernel/kexec_crash_size interface.
*/
-#ifdef CONFIG_KEXEC_CORE
- if (crash_mem_map &&
- !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32)) {
- if (crashk_res.end) {
- __map_memblock(pgdp, crashk_res.start,
- crashk_res.end + 1,
- PAGE_KERNEL,
- NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS);
- memblock_clear_nomap(crashk_res.start,
- resource_size(&crashk_res));
- }
- }
-#endif
}
void mark_rodata_ro(void)
@@ -827,7 +836,6 @@ int kern_addr_valid(unsigned long addr)
return pfn_valid(pte_pfn(pte));
}
-#ifdef CONFIG_MEMORY_HOTPLUG
static void free_hotplug_page_range(struct page *page, size_t size,
struct vmem_altmap *altmap)
{
@@ -863,9 +871,25 @@ static bool pgtable_range_aligned(unsigned long start, unsigned long end,
return true;
}
+static void pte_clear_cont(pte_t *ptep)
+{
+ int i = 0;
+ pte_t pte = READ_ONCE(*ptep);
+ if (pte_none(pte) || !pte_cont(pte))
+ return;
+ ptep -= ((u64)ptep / sizeof(pte_t)) &
+ ((1 << CONFIG_ARM64_CONT_PTE_SHIFT) - 1);
+ do {
+ pte = pte_mknoncont(READ_ONCE(*ptep));
+ set_pte(ptep, pte);
+ } while (++ptep, ++i < CONT_PTES);
+}
+
static void unmap_hotplug_pte_range(pmd_t *pmdp, unsigned long addr,
unsigned long end, bool free_mapped,
- struct vmem_altmap *altmap)
+ struct vmem_altmap *altmap, pgprot_t prot,
+ phys_addr_t (*pgtable_alloc)(int),
+ int flags)
{
pte_t *ptep, pte;
@@ -876,6 +900,8 @@ static void unmap_hotplug_pte_range(pmd_t *pmdp, unsigned long addr,
continue;
WARN_ON(!pte_present(pte));
+
+ pte_clear_cont(ptep);
pte_clear(&init_mm, addr, ptep);
flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
if (free_mapped)
@@ -884,9 +910,26 @@ static void unmap_hotplug_pte_range(pmd_t *pmdp, unsigned long addr,
} while (addr += PAGE_SIZE, addr < end);
}
+static void pmd_clear_cont(pmd_t *pmdp)
+{
+ int i = 0;
+ pmd_t pmd = READ_ONCE(*pmdp);
+ if (pmd_none(pmd) || !pmd_sect(pmd) || !pmd_cont(pmd))
+ return;
+ pmdp -= ((u64)pmdp / sizeof(pmd_t)) &
+ ((1 << CONFIG_ARM64_CONT_PMD_SHIFT) - 1);
+ do {
+ pmd = READ_ONCE(*pmdp);
+ pmd = pte_pmd(pte_mknoncont(pmd_pte(pmd)));
+ set_pmd(pmdp, pmd);
+ } while (++pmdp, ++i < CONT_PMDS);
+}
+
static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
unsigned long end, bool free_mapped,
- struct vmem_altmap *altmap)
+ struct vmem_altmap *altmap, pgprot_t prot,
+ phys_addr_t (*pgtable_alloc)(int),
+ int flags)
{
unsigned long next;
pmd_t *pmdp, pmd;
@@ -900,6 +943,8 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
WARN_ON(!pmd_present(pmd));
if (pmd_sect(pmd)) {
+ //clear CONT flags
+ pmd_clear_cont(pmdp);
pmd_clear(pmdp);
/*
@@ -907,19 +952,36 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
* range is mapped with a single block entry.
*/
flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+
+ if (addr & ~PMD_MASK)
+ alloc_init_cont_pte(pmdp, addr & PMD_MASK,
+ addr, __virt_to_phys(addr &
+ PMD_MASK), prot,
+ pgtable_alloc, flags);
+
+ if (next & ~PMD_MASK)
+ alloc_init_cont_pte(pmdp, next, ALIGN(next,
+ PMD_SIZE),
+ __virt_to_phys(next),
+ prot, pgtable_alloc,
+ flags);
+
if (free_mapped)
free_hotplug_page_range(pmd_page(pmd),
PMD_SIZE, altmap);
continue;
}
WARN_ON(!pmd_table(pmd));
- unmap_hotplug_pte_range(pmdp, addr, next, free_mapped, altmap);
+ unmap_hotplug_pte_range(pmdp, addr, next, free_mapped, altmap,
+ prot, pgtable_alloc, flags);
} while (addr = next, addr < end);
}
static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
unsigned long end, bool free_mapped,
- struct vmem_altmap *altmap)
+ struct vmem_altmap *altmap, pgprot_t prot,
+ phys_addr_t (*pgtable_alloc)(int),
+ int flags)
{
unsigned long next;
pud_t *pudp, pud;
@@ -940,19 +1002,36 @@ static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
* range is mapped with a single block entry.
*/
flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+
+ if (addr & (~PUD_MASK))
+ alloc_init_cont_pmd(pudp, addr & PUD_MASK,
+ addr, __virt_to_phys(addr &
+ PUD_MASK), prot,
+ pgtable_alloc, flags);
+
+ if (next & (~PUD_MASK))
+ alloc_init_cont_pmd(pudp, next,
+ ALIGN(next, PUD_SIZE),
+ __virt_to_phys(next),
+ prot, pgtable_alloc,
+ flags);
+
if (free_mapped)
free_hotplug_page_range(pud_page(pud),
PUD_SIZE, altmap);
continue;
}
WARN_ON(!pud_table(pud));
- unmap_hotplug_pmd_range(pudp, addr, next, free_mapped, altmap);
+ unmap_hotplug_pmd_range(pudp, addr, next, free_mapped, altmap,
+ prot, pgtable_alloc, flags);
} while (addr = next, addr < end);
}
static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr,
unsigned long end, bool free_mapped,
- struct vmem_altmap *altmap)
+ struct vmem_altmap *altmap, pgprot_t prot,
+ phys_addr_t (*pgtable_alloc)(int),
+ int flags)
{
unsigned long next;
p4d_t *p4dp, p4d;
@@ -965,12 +1044,15 @@ static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr,
continue;
WARN_ON(!p4d_present(p4d));
- unmap_hotplug_pud_range(p4dp, addr, next, free_mapped, altmap);
+ unmap_hotplug_pud_range(p4dp, addr, next, free_mapped, altmap,
+ prot, pgtable_alloc, flags);
} while (addr = next, addr < end);
}
static void unmap_hotplug_range(unsigned long addr, unsigned long end,
- bool free_mapped, struct vmem_altmap *altmap)
+ bool free_mapped, struct vmem_altmap *altmap,
+ pgprot_t prot,
+ phys_addr_t (*pgtable_alloc)(int), int flags)
{
unsigned long next;
pgd_t *pgdp, pgd;
@@ -991,7 +1073,8 @@ static void unmap_hotplug_range(unsigned long addr, unsigned long end,
continue;
WARN_ON(!pgd_present(pgd));
- unmap_hotplug_p4d_range(pgdp, addr, next, free_mapped, altmap);
+ unmap_hotplug_p4d_range(pgdp, addr, next, free_mapped, altmap,
+ prot, pgtable_alloc, flags);
} while (addr = next, addr < end);
}
@@ -1148,7 +1231,6 @@ static void free_empty_tables(unsigned long addr, unsigned long end,
free_empty_p4d_table(pgdp, addr, next, floor, ceiling);
} while (addr = next, addr < end);
}
-#endif
#if !ARM64_KERNEL_USES_PMD_MAPS
int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
@@ -1210,7 +1292,7 @@ void vmemmap_free(unsigned long start, unsigned long end,
{
WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END));
- unmap_hotplug_range(start, end, true, altmap);
+ unmap_hotplug_range(start, end, true, altmap, __pgprot(0), NULL, 0);
free_empty_tables(start, end, VMEMMAP_START, VMEMMAP_END);
}
#endif /* CONFIG_MEMORY_HOTPLUG */
@@ -1474,7 +1556,7 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size)
WARN_ON(pgdir != init_mm.pgd);
WARN_ON((start < PAGE_OFFSET) || (end > PAGE_END));
- unmap_hotplug_range(start, end, false, NULL);
+ unmap_hotplug_range(start, end, false, NULL, __pgprot(0), NULL, 0);
free_empty_tables(start, end, PAGE_OFFSET, PAGE_END);
}
--
1.8.3.1
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