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vm: Introduce vm_page_alloc_nofree_domain

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This patch adds a reservation-aware bump allocator intended for
allocating NOFREE pages. The main goal of this change is to reduce the
long-term fragmentation issues caused by pages that are never freed during runtime.

The `vm_page_alloc_nofree_domain` routine hands out 0-order pages from
a preallocated superpage. Once an active NOFREE superpage fills up, the
routine will try to allocate a new one and discard the old one.
This routine will get invoked whenever VM_ALLOC_NOFREE is passed to
vm_page_alloc_noobj or vm_page_alloc.

Differential Revision:	https://reviews.freebsd.org/D45863
Reviewed by:	alc, kib, markj
Tested by:	alc
This commit is contained in:
Bojan Novković 2024-07-14 15:14:22 +02:00
parent 92b9138991
commit a8693e89e3
2 changed files with 66 additions and 0 deletions
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62
sys/vm/vm_page.c
View file

@ -163,6 +163,7 @@ SYSCTL_PROC(_vm, OID_AUTO, page_blacklist, CTLTYPE_STRING | CTLFLAG_RD |
static uma_zone_t fakepg_zone;
static void vm_page_alloc_check(vm_page_t m);
static vm_page_t vm_page_alloc_nofree_domain(int domain, int req);
static bool _vm_page_busy_sleep(vm_object_t obj, vm_page_t m,
vm_pindex_t pindex, const char *wmesg, int allocflags, bool locked);
static void vm_page_clear_dirty_mask(vm_page_t m, vm_page_bits_t pagebits);
@ -2099,6 +2100,11 @@ vm_page_alloc_domain_after(vm_object_t object, vm_pindex_t pindex, int domain,
if (!vm_pager_can_alloc_page(object, pindex))
return (NULL);
again:
if (__predict_false((req & VM_ALLOC_NOFREE) != 0)) {
m = vm_page_alloc_nofree_domain(domain, req);
if (m != NULL)
goto found;
}
#if VM_NRESERVLEVEL > 0
/*
* Can we allocate the page from a reservation?
@ -2430,6 +2436,12 @@ vm_page_alloc_noobj_domain(int domain, int req)
((req & VM_ALLOC_NOFREE) != 0 ? PG_NOFREE : 0);
vmd = VM_DOMAIN(domain);
again:
if (__predict_false((req & VM_ALLOC_NOFREE) != 0)) {
m = vm_page_alloc_nofree_domain(domain, req);
if (m != NULL)
goto found;
}
if (vmd->vmd_pgcache[VM_FREEPOOL_DIRECT].zone != NULL) {
m = uma_zalloc(vmd->vmd_pgcache[VM_FREEPOOL_DIRECT].zone,
M_NOWAIT | M_NOVM);
@ -2480,6 +2492,56 @@ found:
return (m);
}
#if VM_NRESERVLEVEL > 1
#define VM_NOFREE_IMPORT_ORDER (VM_LEVEL_1_ORDER + VM_LEVEL_0_ORDER)
#elif VM_NRESERVLEVEL > 0
#define VM_NOFREE_IMPORT_ORDER VM_LEVEL_0_ORDER
#else
#define VM_NOFREE_IMPORT_ORDER 8
#endif
/*
* Allocate a single NOFREE page.
*
* This routine hands out NOFREE pages from higher-order
* physical memory blocks in order to reduce memory fragmentation.
* When a NOFREE for a given domain chunk is used up,
* the routine will try to fetch a new one from the freelists
* and discard the old one.
*/
static vm_page_t
vm_page_alloc_nofree_domain(int domain, int req)
{
vm_page_t m;
struct vm_domain *vmd;
struct vm_nofreeq *nqp;
KASSERT((req & VM_ALLOC_NOFREE) != 0, ("invalid request %#x", req));
vmd = VM_DOMAIN(domain);
nqp = &vmd->vmd_nofreeq;
vm_domain_free_lock(vmd);
if (nqp->offs >= (1 << VM_NOFREE_IMPORT_ORDER) || nqp->ma == NULL) {
if (!vm_domain_allocate(vmd, req,
1 << VM_NOFREE_IMPORT_ORDER)) {
vm_domain_free_unlock(vmd);
return (NULL);
}
nqp->ma = vm_phys_alloc_pages(domain, VM_FREEPOOL_DEFAULT,
VM_LEVEL_0_ORDER);
if (nqp->ma == NULL) {
vm_domain_freecnt_inc(vmd, 1 << VM_NOFREE_IMPORT_ORDER);
vm_domain_free_unlock(vmd);
return (NULL);
}
nqp->offs = 0;
}
m = &nqp->ma[nqp->offs++];
vm_domain_free_unlock(vmd);
return (m);
}
vm_page_t
vm_page_alloc_noobj(int req)
{

4
sys/vm/vm_pagequeue.h
View file

@ -246,6 +246,10 @@ struct vm_domain {
u_int vmd_domain; /* (c) Domain number. */
u_int vmd_page_count; /* (c) Total page count. */
long vmd_segs; /* (c) bitmask of the segments */
struct vm_nofreeq {
vm_page_t ma;
int offs;
} vmd_nofreeq; /* (f) NOFREE page bump allocator. */
u_int __aligned(CACHE_LINE_SIZE) vmd_free_count; /* (a,f) free page count */
u_int vmd_pageout_deficit; /* (a) Estimated number of pages deficit */
uint8_t vmd_pad[CACHE_LINE_SIZE - (sizeof(u_int) * 2)];