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Use a single VM object for kernel stacks.

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Previously we allocated a separate VM object for each kernel stack.
However, fully constructed kernel stacks are cached by UMA, so there is
no harm in using a single global object for all stacks.  This reduces
memory consumption and makes it easier to define a memory allocation
policy for kernel stack pages, with the aim of reducing physical memory
fragmentation.

Add a global kstack_object, and use the stack KVA address to index into
the object like we do with kernel_object.

Reviewed by:	kib
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D24473
This commit is contained in:
Mark Johnston 2020-04-26 20:08:57 +00:00
parent 1130dff9d2
commit f13fa9df05
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=360354
6 changed files with 73 additions and 69 deletions
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2
sys/kern/kern_thread.c
View File

@ -84,7 +84,7 @@ _Static_assert(offsetof(struct thread, td_pflags) == 0x104,
"struct thread KBI td_pflags");
_Static_assert(offsetof(struct thread, td_frame) == 0x498,
"struct thread KBI td_frame");
_Static_assert(offsetof(struct thread, td_emuldata) == 0x6b0,
_Static_assert(offsetof(struct thread, td_emuldata) == 0x6a0,
"struct thread KBI td_emuldata");
_Static_assert(offsetof(struct proc, p_flag) == 0xb0,
"struct proc KBI p_flag");

1
sys/sys/proc.h
View File

@ -348,7 +348,6 @@ struct thread {
/* LP64 hole */
struct callout td_slpcallout; /* (h) Callout for sleep. */
struct trapframe *td_frame; /* (k) */
struct vm_object *td_kstack_obj;/* (a) Kstack object. */
vm_offset_t td_kstack; /* (a) Kernel VA of kstack. */
int td_kstack_pages; /* (a) Size of the kstack. */
volatile u_int td_critnest; /* (k*) Critical section nest level. */

2
sys/vm/vm_extern.h
View File

@ -126,6 +126,8 @@ struct sf_buf *vm_imgact_map_page(vm_object_t object, vm_ooffset_t offset);
void vm_imgact_unmap_page(struct sf_buf *sf);
void vm_thread_dispose(struct thread *td);
int vm_thread_new(struct thread *td, int pages);
void vm_thread_stack_back(struct domainset *ds, vm_offset_t kaddr,
vm_page_t ma[], int npages, int req_class);
u_int vm_active_count(void);
u_int vm_inactive_count(void);
u_int vm_laundry_count(void);

97
sys/vm/vm_glue.c
View File

@ -264,9 +264,9 @@ vm_sync_icache(vm_map_t map, vm_offset_t va, vm_offset_t sz)
pmap_sync_icache(map->pmap, va, sz);
}
vm_object_t kstack_object;
static uma_zone_t kstack_cache;
static int kstack_cache_size;
static int kstack_domain_iter;
static int
sysctl_kstack_cache_size(SYSCTL_HANDLER_ARGS)
@ -285,22 +285,14 @@ SYSCTL_PROC(_vm, OID_AUTO, kstack_cache_size,
/*
* Create the kernel stack (including pcb for i386) for a new thread.
* This routine directly affects the fork perf for a process and
* create performance for a thread.
*/
static vm_offset_t
vm_thread_stack_create(struct domainset *ds, vm_object_t *ksobjp, int pages)
vm_thread_stack_create(struct domainset *ds, int pages)
{
vm_page_t ma[KSTACK_MAX_PAGES];
vm_object_t ksobj;
vm_offset_t ks;
int i;
/*
* Allocate an object for the kstack.
*/
ksobj = vm_object_allocate(OBJT_DEFAULT, pages);
/*
* Get a kernel virtual address for this thread's kstack.
*/
@ -319,54 +311,45 @@ vm_thread_stack_create(struct domainset *ds, vm_object_t *ksobjp, int pages)
#endif
if (ks == 0) {
printf("%s: kstack allocation failed\n", __func__);
vm_object_deallocate(ksobj);
return (0);
}
if (vm_ndomains > 1) {
ksobj->domain.dr_policy = ds;
ksobj->domain.dr_iter =
atomic_fetchadd_int(&kstack_domain_iter, 1);
}
if (KSTACK_GUARD_PAGES != 0) {
pmap_qremove(ks, KSTACK_GUARD_PAGES);
ks += KSTACK_GUARD_PAGES * PAGE_SIZE;
}
/*
* For the length of the stack, link in a real page of ram for each
* page of stack.
/*
* Allocate physical pages to back the stack.
*/
VM_OBJECT_WLOCK(ksobj);
(void)vm_page_grab_pages(ksobj, 0, VM_ALLOC_NORMAL | VM_ALLOC_WIRED,
ma, pages);
vm_thread_stack_back(ds, ks, ma, pages, VM_ALLOC_NORMAL);
for (i = 0; i < pages; i++)
vm_page_valid(ma[i]);
VM_OBJECT_WUNLOCK(ksobj);
pmap_qenter(ks, ma, pages);
*ksobjp = ksobj;
return (ks);
}
static void
vm_thread_stack_dispose(vm_object_t ksobj, vm_offset_t ks, int pages)
vm_thread_stack_dispose(vm_offset_t ks, int pages)
{
vm_page_t m;
vm_pindex_t pindex;
int i;
pindex = atop(ks - VM_MIN_KERNEL_ADDRESS);
pmap_qremove(ks, pages);
VM_OBJECT_WLOCK(ksobj);
VM_OBJECT_WLOCK(kstack_object);
for (i = 0; i < pages; i++) {
m = vm_page_lookup(ksobj, i);
m = vm_page_lookup(kstack_object, pindex + i);
if (m == NULL)
panic("%s: kstack already missing?", __func__);
vm_page_xbusy_claim(m);
vm_page_unwire_noq(m);
vm_page_free(m);
}
VM_OBJECT_WUNLOCK(ksobj);
vm_object_deallocate(ksobj);
VM_OBJECT_WUNLOCK(kstack_object);
kva_free(ks - (KSTACK_GUARD_PAGES * PAGE_SIZE),
(pages + KSTACK_GUARD_PAGES) * PAGE_SIZE);
}
@ -377,7 +360,6 @@ vm_thread_stack_dispose(vm_object_t ksobj, vm_offset_t ks, int pages)
int
vm_thread_new(struct thread *td, int pages)
{
vm_object_t ksobj;
vm_offset_t ks;
/* Bounds check */
@ -387,12 +369,8 @@ vm_thread_new(struct thread *td, int pages)
pages = KSTACK_MAX_PAGES;
ks = 0;
ksobj = NULL;
if (pages == kstack_pages && kstack_cache != NULL) {
if (pages == kstack_pages && kstack_cache != NULL)
ks = (vm_offset_t)uma_zalloc(kstack_cache, M_NOWAIT);
if (ks != 0)
ksobj = PHYS_TO_VM_PAGE(pmap_kextract(ks))->object;
}
/*
* Ensure that kstack objects can draw pages from any memory
@ -401,10 +379,9 @@ vm_thread_new(struct thread *td, int pages)
*/
if (ks == 0)
ks = vm_thread_stack_create(DOMAINSET_PREF(PCPU_GET(domain)),
&ksobj, pages);
pages);
if (ks == 0)
return (0);
td->td_kstack_obj = ksobj;
td->td_kstack = ks;
td->td_kstack_pages = pages;
return (1);
@ -416,26 +393,52 @@ vm_thread_new(struct thread *td, int pages)
void
vm_thread_dispose(struct thread *td)
{
vm_object_t ksobj;
vm_offset_t ks;
int pages;
pages = td->td_kstack_pages;
ksobj = td->td_kstack_obj;
ks = td->td_kstack;
td->td_kstack = 0;
td->td_kstack_pages = 0;
if (pages == kstack_pages)
uma_zfree(kstack_cache, (void *)ks);
else
vm_thread_stack_dispose(ksobj, ks, pages);
vm_thread_stack_dispose(ks, pages);
}
/*
* Allocate physical pages, following the specified NUMA policy, to back a
* kernel stack.
*/
void
vm_thread_stack_back(struct domainset *ds, vm_offset_t ks, vm_page_t ma[],
int npages, int req_class)
{
vm_pindex_t pindex;
int n;
pindex = atop(ks - VM_MIN_KERNEL_ADDRESS);
VM_OBJECT_WLOCK(kstack_object);
for (n = 0; n < npages;) {
if (vm_ndomains > 1)
kstack_object->domain.dr_policy = ds;
/*
* Use WAITFAIL to force a reset of the domain selection policy
* if we had to sleep for pages.
*/
n += vm_page_grab_pages(kstack_object, pindex + n,
req_class | VM_ALLOC_WIRED | VM_ALLOC_WAITFAIL,
&ma[n], npages - n);
}
VM_OBJECT_WUNLOCK(kstack_object);
}
static int
kstack_import(void *arg, void **store, int cnt, int domain, int flags)
{
struct domainset *ds;
vm_object_t ksobj;
int i;
if (domain == UMA_ANYDOMAIN)
@ -444,8 +447,7 @@ kstack_import(void *arg, void **store, int cnt, int domain, int flags)
ds = DOMAINSET_PREF(domain);
for (i = 0; i < cnt; i++) {
store[i] = (void *)vm_thread_stack_create(ds, &ksobj,
kstack_pages);
store[i] = (void *)vm_thread_stack_create(ds, kstack_pages);
if (store[i] == NULL)
break;
}
@ -460,15 +462,15 @@ kstack_release(void *arg, void **store, int cnt)
for (i = 0; i < cnt; i++) {
ks = (vm_offset_t)store[i];
vm_thread_stack_dispose(
PHYS_TO_VM_PAGE(pmap_kextract(ks))->object,
ks, kstack_pages);
vm_thread_stack_dispose(ks, kstack_pages);
}
}
static void
kstack_cache_init(void *null)
{
kstack_object = vm_object_allocate(OBJT_SWAP,
atop(VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS));
kstack_cache = uma_zcache_create("kstack_cache",
kstack_pages * PAGE_SIZE, NULL, NULL, NULL, NULL,
kstack_import, kstack_release, NULL,
@ -476,8 +478,7 @@ kstack_cache_init(void *null)
kstack_cache_size = imax(128, mp_ncpus * 4);
uma_zone_set_maxcache(kstack_cache, kstack_cache_size);
}
SYSINIT(vm_kstacks, SI_SUB_KTHREAD_INIT, SI_ORDER_ANY, kstack_cache_init, NULL);
SYSINIT(vm_kstacks, SI_SUB_KMEM, SI_ORDER_ANY, kstack_cache_init, NULL);
#ifdef KSTACK_USAGE_PROF
/*

1
sys/vm/vm_kern.h
View File

@ -77,5 +77,6 @@ extern struct vmem *memguard_arena;
extern u_long vm_kmem_size;
extern u_int exec_map_entries;
extern u_int exec_map_entry_size;
extern vm_object_t kstack_object;
#endif /* _VM_VM_KERN_H_ */

39
sys/vm/vm_swapout.c
View File

@ -104,6 +104,7 @@ __FBSDID("$FreeBSD$");
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
@ -526,24 +527,26 @@ vm_daemon(void)
static void
vm_thread_swapout(struct thread *td)
{
vm_object_t ksobj;
vm_page_t m;
vm_offset_t kaddr;
vm_pindex_t pindex;
int i, pages;
cpu_thread_swapout(td);
kaddr = td->td_kstack;
pages = td->td_kstack_pages;
ksobj = td->td_kstack_obj;
pmap_qremove(td->td_kstack, pages);
VM_OBJECT_WLOCK(ksobj);
pindex = atop(kaddr - VM_MIN_KERNEL_ADDRESS);
pmap_qremove(kaddr, pages);
VM_OBJECT_WLOCK(kstack_object);
for (i = 0; i < pages; i++) {
m = vm_page_lookup(ksobj, i);
m = vm_page_lookup(kstack_object, pindex + i);
if (m == NULL)
panic("vm_thread_swapout: kstack already missing?");
vm_page_dirty(m);
vm_page_xunbusy_unchecked(m);
vm_page_unwire(m, PQ_LAUNDRY);
}
VM_OBJECT_WUNLOCK(ksobj);
VM_OBJECT_WUNLOCK(kstack_object);
}
/*
@ -552,38 +555,36 @@ vm_thread_swapout(struct thread *td)
static void
vm_thread_swapin(struct thread *td, int oom_alloc)
{
vm_object_t ksobj;
vm_page_t ma[KSTACK_MAX_PAGES];
vm_offset_t kaddr;
int a, count, i, j, pages, rv;
kaddr = td->td_kstack;
pages = td->td_kstack_pages;
ksobj = td->td_kstack_obj;
VM_OBJECT_WLOCK(ksobj);
(void)vm_page_grab_pages(ksobj, 0, oom_alloc | VM_ALLOC_WIRED, ma,
pages);
VM_OBJECT_WUNLOCK(ksobj);
vm_thread_stack_back(td->td_domain.dr_policy, kaddr, ma, pages,
oom_alloc);
for (i = 0; i < pages;) {
vm_page_assert_xbusied(ma[i]);
if (vm_page_all_valid(ma[i])) {
i++;
continue;
}
vm_object_pip_add(ksobj, 1);
vm_object_pip_add(kstack_object, 1);
for (j = i + 1; j < pages; j++)
if (vm_page_all_valid(ma[j]))
break;
VM_OBJECT_WLOCK(ksobj);
rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a);
VM_OBJECT_WUNLOCK(ksobj);
VM_OBJECT_WLOCK(kstack_object);
rv = vm_pager_has_page(kstack_object, ma[i]->pindex, NULL, &a);
VM_OBJECT_WUNLOCK(kstack_object);
KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
count = min(a + 1, j - i);
rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL);
rv = vm_pager_get_pages(kstack_object, ma + i, count, NULL, NULL);
KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
__func__, td->td_proc->p_pid));
vm_object_pip_wakeup(ksobj);
vm_object_pip_wakeup(kstack_object);
i += count;
}
pmap_qenter(td->td_kstack, ma, pages);
pmap_qenter(kaddr, ma, pages);
cpu_thread_swapin(td);
}