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mm: remove vmacache 

By using the maple tree and the maple tree state, the vmacache is no
longer beneficial and is complicating the VMA code.  Remove the vmacache
to reduce the work in keeping it up to date and code complexity.

Link: https://lkml.kernel.org/r/20220906194824.2110408-26-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett 2022-09-06 19:48:51 +00:00 committed by Andrew Morton
parent 4dd1b84140
commit 7964cf8caa
17 changed files with 9 additions and 267 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/exec.c
View File

@ -28,7 +28,6 @@
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/swap.h>
@ -1027,8 +1026,6 @@ static int exec_mmap(struct mm_struct *mm)
activate_mm(active_mm, mm);
if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
local_irq_enable();
tsk->mm->vmacache_seqnum = 0;
vmacache_flush(tsk);
task_unlock(tsk);
lru_gen_use_mm(mm);

1
fs/proc/task_mmu.c
View File

@ -1,6 +1,5 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/pagewalk.h>
#include <linux/vmacache.h>
#include <linux/mm_inline.h>
#include <linux/hugetlb.h>
#include <linux/huge_mm.h>

1
include/linux/mm_types.h
View File

@ -475,7 +475,6 @@ struct mm_struct {
struct {
struct vm_area_struct *mmap; /* list of VMAs */
struct maple_tree mm_mt;
u64 vmacache_seqnum; /* per-thread vmacache */
#ifdef CONFIG_MMU
unsigned long (*get_unmapped_area) (struct file *filp,
unsigned long addr, unsigned long len,

12
include/linux/mm_types_task.h
View File

@ -24,18 +24,6 @@
IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
/*
* The per task VMA cache array:
*/
#define VMACACHE_BITS 2
#define VMACACHE_SIZE (1U << VMACACHE_BITS)
#define VMACACHE_MASK (VMACACHE_SIZE - 1)
struct vmacache {
u64 seqnum;
struct vm_area_struct *vmas[VMACACHE_SIZE];
};
/*
* When updating this, please also update struct resident_page_types[] in
* kernel/fork.c

1
include/linux/sched.h
View File

@ -861,7 +861,6 @@ struct task_struct {
struct mm_struct *active_mm;
/* Per-thread vma caching: */
struct vmacache vmacache;
#ifdef SPLIT_RSS_COUNTING
struct task_rss_stat rss_stat;

4
include/linux/vm_event_item.h
View File

@ -129,10 +129,6 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
NR_TLB_LOCAL_FLUSH_ALL,
NR_TLB_LOCAL_FLUSH_ONE,
#endif /* CONFIG_DEBUG_TLBFLUSH */
#ifdef CONFIG_DEBUG_VM_VMACACHE
VMACACHE_FIND_CALLS,
VMACACHE_FIND_HITS,
#endif
#ifdef CONFIG_SWAP
SWAP_RA,
SWAP_RA_HIT,

28
include/linux/vmacache.h
View File

@ -1,28 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_VMACACHE_H
#define __LINUX_VMACACHE_H
#include <linux/sched.h>
#include <linux/mm.h>
static inline void vmacache_flush(struct task_struct *tsk)
{
memset(tsk->vmacache.vmas, 0, sizeof(tsk->vmacache.vmas));
}
extern void vmacache_update(unsigned long addr, struct vm_area_struct *newvma);
extern struct vm_area_struct *vmacache_find(struct mm_struct *mm,
unsigned long addr);
#ifndef CONFIG_MMU
extern struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
unsigned long start,
unsigned long end);
#endif
static inline void vmacache_invalidate(struct mm_struct *mm)
{
mm->vmacache_seqnum++;
}
#endif /* __LINUX_VMACACHE_H */

6
include/linux/vmstat.h
View File

@ -125,12 +125,6 @@ static inline void vm_events_fold_cpu(int cpu)
#define count_vm_tlb_events(x, y) do { (void)(y); } while (0)
#endif
#ifdef CONFIG_DEBUG_VM_VMACACHE
#define count_vm_vmacache_event(x) count_vm_event(x)
#else
#define count_vm_vmacache_event(x) do {} while (0)
#endif
#define __count_zid_vm_events(item, zid, delta) \
__count_vm_events(item##_NORMAL - ZONE_NORMAL + zid, delta)

12
kernel/debug/debug_core.c
View File

@ -50,7 +50,6 @@
#include <linux/pid.h>
#include <linux/smp.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
#include <linux/rcupdate.h>
#include <linux/irq.h>
#include <linux/security.h>
@ -283,17 +282,6 @@ static void kgdb_flush_swbreak_addr(unsigned long addr)
if (!CACHE_FLUSH_IS_SAFE)
return;
if (current->mm) {
int i;
for (i = 0; i < VMACACHE_SIZE; i++) {
if (!current->vmacache.vmas[i])
continue;
flush_cache_range(current->vmacache.vmas[i],
addr, addr + BREAK_INSTR_SIZE);
}
}
/* Force flush instruction cache if it was outside the mm */
flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
}

5
kernel/fork.c
View File

@ -43,7 +43,6 @@
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/vmacache.h>
#include <linux/nsproxy.h>
#include <linux/capability.h>
#include <linux/cpu.h>
@ -1128,7 +1127,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm->mmap = NULL;
mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
mm->vmacache_seqnum = 0;
atomic_set(&mm->mm_users, 1);
atomic_set(&mm->mm_count, 1);
seqcount_init(&mm->write_protect_seq);
@ -1585,9 +1583,6 @@ static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
if (!oldmm)
return 0;
/* initialize the new vmacache entries */
vmacache_flush(tsk);
if (clone_flags & CLONE_VM) {
mmget(oldmm);
mm = oldmm;

8
lib/Kconfig.debug
View File

@ -812,14 +812,6 @@ config DEBUG_VM
If unsure, say N.
config DEBUG_VM_VMACACHE
bool "Debug VMA caching"
depends on DEBUG_VM
help
Enable this to turn on VMA caching debug information. Doing so
can cause significant overhead, so only enable it in non-production
environments.
config DEBUG_VM_MAPLE_TREE
bool "Debug VM maple trees"
depends on DEBUG_VM

2
mm/Makefile
View File

@ -52,7 +52,7 @@ obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
readahead.o swap.o truncate.o vmscan.o shmem.o \
util.o mmzone.o vmstat.o backing-dev.o \
mm_init.o percpu.o slab_common.o \
compaction.o vmacache.o \
compaction.o \
interval_tree.o list_lru.o workingset.o \
debug.o gup.o mmap_lock.o $(mmu-y)

4
mm/debug.c
View File

@ -155,7 +155,7 @@ EXPORT_SYMBOL(dump_vma);
void dump_mm(const struct mm_struct *mm)
{
pr_emerg("mm %px mmap %px seqnum %llu task_size %lu\n"
pr_emerg("mm %px mmap %px task_size %lu\n"
#ifdef CONFIG_MMU
"get_unmapped_area %px\n"
#endif
@ -183,7 +183,7 @@ void dump_mm(const struct mm_struct *mm)
"tlb_flush_pending %d\n"
"def_flags: %#lx(%pGv)\n",
mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size,
mm, mm->mmap, mm->task_size,
#ifdef CONFIG_MMU
mm->get_unmapped_area,
#endif

31
mm/mmap.c
View File

@ -14,7 +14,6 @@
#include <linux/backing-dev.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/vmacache.h>
#include <linux/shm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
@ -680,9 +679,6 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
/* Remove from mm linked list - also updates highest_vm_end */
__vma_unlink_list(mm, next);
/* Kill the cache */
vmacache_invalidate(mm);
if (file)
__remove_shared_vm_struct(next, file, mapping);
@ -923,8 +919,6 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
__vma_unlink_list(mm, next);
if (remove_next == 2)
__vma_unlink_list(mm, next_next);
/* Kill the cache */
vmacache_invalidate(mm);
if (file) {
__remove_shared_vm_struct(next, file, mapping);
@ -2233,19 +2227,10 @@ struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
unsigned long start_addr,
unsigned long end_addr)
{
struct vm_area_struct *vma;
unsigned long index = start_addr;
mmap_assert_locked(mm);
/* Check the cache first. */
vma = vmacache_find(mm, start_addr);
if (likely(vma))
return vma;
vma = mt_find(&mm->mm_mt, &index, end_addr - 1);
if (vma)
vmacache_update(start_addr, vma);
return vma;
return mt_find(&mm->mm_mt, &index, end_addr - 1);
}
EXPORT_SYMBOL(find_vma_intersection);
@ -2259,19 +2244,10 @@ EXPORT_SYMBOL(find_vma_intersection);
*/
struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
{
struct vm_area_struct *vma;
unsigned long index = addr;
mmap_assert_locked(mm);
/* Check the cache first. */
vma = vmacache_find(mm, addr);
if (likely(vma))
return vma;
vma = mt_find(&mm->mm_mt, &index, ULONG_MAX);
if (vma)
vmacache_update(addr, vma);
return vma;
return mt_find(&mm->mm_mt, &index, ULONG_MAX);
}
EXPORT_SYMBOL(find_vma);
@ -2660,9 +2636,6 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct ma_state *mas,
mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
tail_vma->vm_next = NULL;
/* Kill the cache */
vmacache_invalidate(mm);
/*
* Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
* VM_GROWSUP VMA. Such VMAs can change their size under

37
mm/nommu.c
View File

@ -19,7 +19,6 @@
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/vmacache.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/file.h>
@ -598,23 +597,12 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
*/
static void delete_vma_from_mm(struct vm_area_struct *vma)
{
int i;
struct address_space *mapping;
struct mm_struct *mm = vma->vm_mm;
struct task_struct *curr = current;
MA_STATE(mas, &vma->vm_mm->mm_mt, 0, 0);
mm->map_count--;
for (i = 0; i < VMACACHE_SIZE; i++) {
/* if the vma is cached, invalidate the entire cache */
if (curr->vmacache.vmas[i] == vma) {
vmacache_invalidate(mm);
break;
}
}
vma->vm_mm->map_count--;
/* remove the VMA from the mapping */
if (vma->vm_file) {
struct address_space *mapping;
mapping = vma->vm_file->f_mapping;
i_mmap_lock_write(mapping);
@ -626,7 +614,7 @@ static void delete_vma_from_mm(struct vm_area_struct *vma)
/* remove from the MM's tree and list */
vma_mas_remove(vma, &mas);
__vma_unlink_list(mm, vma);
__vma_unlink_list(vma->vm_mm, vma);
}
/*
@ -659,20 +647,9 @@ EXPORT_SYMBOL(find_vma_intersection);
*/
struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
{
struct vm_area_struct *vma;
MA_STATE(mas, &mm->mm_mt, addr, addr);
/* check the cache first */
vma = vmacache_find(mm, addr);
if (likely(vma))
return vma;
vma = mas_walk(&mas);
if (vma)
vmacache_update(addr, vma);
return vma;
return mas_walk(&mas);
}
EXPORT_SYMBOL(find_vma);
@ -706,11 +683,6 @@ static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
unsigned long end = addr + len;
MA_STATE(mas, &mm->mm_mt, addr, addr);
/* check the cache first */
vma = vmacache_find_exact(mm, addr, end);
if (vma)
return vma;
vma = mas_walk(&mas);
if (!vma)
return NULL;
@ -719,7 +691,6 @@ static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
if (vma->vm_end != end)
return NULL;
vmacache_update(addr, vma);
return vma;
}

117
mm/vmacache.c
View File

@ -1,117 +0,0 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2014 Davidlohr Bueso.
*/
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
/*
* Hash based on the pmd of addr if configured with MMU, which provides a good
* hit rate for workloads with spatial locality. Otherwise, use pages.
*/
#ifdef CONFIG_MMU
#define VMACACHE_SHIFT PMD_SHIFT
#else
#define VMACACHE_SHIFT PAGE_SHIFT
#endif
#define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
/*
* This task may be accessing a foreign mm via (for example)
* get_user_pages()->find_vma(). The vmacache is task-local and this
* task's vmacache pertains to a different mm (ie, its own). There is
* nothing we can do here.
*
* Also handle the case where a kernel thread has adopted this mm via
* kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
*/
static inline bool vmacache_valid_mm(struct mm_struct *mm)
{
return current->mm == mm && !(current->flags & PF_KTHREAD);
}
void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
{
if (vmacache_valid_mm(newvma->vm_mm))
current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
}
static bool vmacache_valid(struct mm_struct *mm)
{
struct task_struct *curr;
if (!vmacache_valid_mm(mm))
return false;
curr = current;
if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
/*
* First attempt will always be invalid, initialize
* the new cache for this task here.
*/
curr->vmacache.seqnum = mm->vmacache_seqnum;
vmacache_flush(curr);
return false;
}
return true;
}
struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
{
int idx = VMACACHE_HASH(addr);
int i;
count_vm_vmacache_event(VMACACHE_FIND_CALLS);
if (!vmacache_valid(mm))
return NULL;
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache.vmas[idx];
if (vma) {
#ifdef CONFIG_DEBUG_VM_VMACACHE
if (WARN_ON_ONCE(vma->vm_mm != mm))
break;
#endif
if (vma->vm_start <= addr && vma->vm_end > addr) {
count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
}
}
if (++idx == VMACACHE_SIZE)
idx = 0;
}
return NULL;
}
#ifndef CONFIG_MMU
struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
unsigned long start,
unsigned long end)
{
int idx = VMACACHE_HASH(start);
int i;
count_vm_vmacache_event(VMACACHE_FIND_CALLS);
if (!vmacache_valid(mm))
return NULL;
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache.vmas[idx];
if (vma && vma->vm_start == start && vma->vm_end == end) {
count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
}
if (++idx == VMACACHE_SIZE)
idx = 0;
}
return NULL;
}
#endif

4
mm/vmstat.c
View File

@ -1389,10 +1389,6 @@ const char * const vmstat_text[] = {
"nr_tlb_local_flush_one",
#endif /* CONFIG_DEBUG_TLBFLUSH */
#ifdef CONFIG_DEBUG_VM_VMACACHE
"vmacache_find_calls",
"vmacache_find_hits",
#endif
#ifdef CONFIG_SWAP
"swap_ra",
"swap_ra_hit",