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vm_phys: avoid waste in multipage allocation

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In vm_phys_alloc_contig, for an allocation bigger than the size of any
buddy queue free block, avoid examining any maximum-size free block
more than twice, by only starting to consider a sequence of adjacent
max-blocks starting at a max-block that does not follow another
max-block.  If that first max-block follows adjacent blocks of smaller
size, and if together they provide enough memory to reduce by one the
number of max-blocks required for this allocation, use them as part of
this allocation.

Reviewed by:	markj
Tested by:	pho
Discussed with:	alc
Differential Revision:	https://reviews.freebsd.org/D34815
This commit is contained in:
Doug Moore 2022-04-26 02:56:23 -05:00
parent 651a887f4e
commit fa8a6585c7
1 changed files with 146 additions and 75 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

221
sys/vm/vm_phys.c
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@ -1354,20 +1354,125 @@ vm_phys_unfree_page(vm_page_t m)
} }
/* /*
* Allocate a run of contiguous physical pages from the specified free list * Find a run of contiguous physical pages from the specified page list.
*/
static vm_page_t
vm_phys_find_freelist_contig(struct vm_freelist *fl, int oind, u_long npages,
vm_paddr_t low, vm_paddr_t high, u_long alignment, vm_paddr_t boundary)
{
struct vm_phys_seg *seg;
vm_paddr_t frag, lbound, pa, page_size, pa_end, pa_pre, size;
vm_page_t m, m_listed, m_ret;
int order;
KASSERT(npages > 0, ("npages is 0"));
KASSERT(powerof2(alignment), ("alignment is not a power of 2"));
KASSERT(powerof2(boundary), ("boundary is not a power of 2"));
/* Search for a run satisfying the specified conditions. */
page_size = PAGE_SIZE;
size = npages << PAGE_SHIFT;
frag = (npages & ~(~0UL << oind)) << PAGE_SHIFT;
TAILQ_FOREACH(m_listed, &fl[oind].pl, listq) {
/*
* Determine if the address range starting at pa is
* too low.
*/
pa = VM_PAGE_TO_PHYS(m_listed);
if (pa < low)
continue;
/*
* If this is not the first free oind-block in this range, bail
* out. We have seen the first free block already, or will see
* it before failing to find an appropriate range.
*/
seg = &vm_phys_segs[m_listed->segind];
lbound = low > seg->start ? low : seg->start;
pa_pre = pa - (page_size << oind);
m = &seg->first_page[atop(pa_pre - seg->start)];
if (pa != 0 && pa_pre >= lbound && m->order == oind)
continue;
if (!vm_addr_align_ok(pa, alignment))
/* Advance to satisfy alignment condition. */
pa = roundup2(pa, alignment);
else if (frag != 0 && lbound + frag <= pa) {
/*
* Back up to the first aligned free block in this
* range, without moving below lbound.
*/
pa_end = pa;
for (order = oind - 1; order >= 0; order--) {
pa_pre = pa_end - (page_size << order);
if (!vm_addr_align_ok(pa_pre, alignment))
break;
m = &seg->first_page[atop(pa_pre - seg->start)];
if (pa_pre >= lbound && m->order == order)
pa_end = pa_pre;
}
/*
* If the extra small blocks are enough to complete the
* fragment, use them. Otherwise, look to allocate the
* fragment at the other end.
*/
if (pa_end + frag <= pa)
pa = pa_end;
}
/* Advance as necessary to satisfy boundary conditions. */
if (!vm_addr_bound_ok(pa, size, boundary))
pa = roundup2(pa + 1, boundary);
pa_end = pa + size;
/*
* Determine if the address range is valid (without overflow in
* pa_end calculation), and fits within the segment.
*/
if (pa_end < pa || seg->end < pa_end)
continue;
m_ret = &seg->first_page[atop(pa - seg->start)];
/*
* Determine whether there are enough free oind-blocks here to
* satisfy the allocation request.
*/
pa = VM_PAGE_TO_PHYS(m_listed);
do {
pa += page_size << oind;
if (pa >= pa_end)
return (m_ret);
m = &seg->first_page[atop(pa - seg->start)];
} while (oind == m->order);
/*
* Determine if an additional series of free blocks of
* diminishing size can help to satisfy the allocation request.
*/
while (m->order < oind &&
pa + 2 * (page_size << m->order) > pa_end) {
pa += page_size << m->order;
if (pa >= pa_end)
return (m_ret);
m = &seg->first_page[atop(pa - seg->start)];
}
}
return (NULL);
}
/*
* Find a run of contiguous physical pages from the specified free list
* table. * table.
*/ */
static vm_page_t static vm_page_t
vm_phys_alloc_queues_contig( vm_phys_find_queues_contig(
struct vm_freelist (*queues)[VM_NFREEPOOL][VM_NFREEORDER_MAX], struct vm_freelist (*queues)[VM_NFREEPOOL][VM_NFREEORDER_MAX],
u_long npages, vm_paddr_t low, vm_paddr_t high, u_long npages, vm_paddr_t low, vm_paddr_t high,
u_long alignment, vm_paddr_t boundary) u_long alignment, vm_paddr_t boundary)
{ {
struct vm_phys_seg *seg;
struct vm_freelist *fl; struct vm_freelist *fl;
vm_page_t m_ret;
vm_paddr_t pa, pa_end, size; vm_paddr_t pa, pa_end, size;
vm_page_t m, m_ret;
u_long npages_end;
int oind, order, pind; int oind, order, pind;
KASSERT(npages > 0, ("npages is 0")); KASSERT(npages > 0, ("npages is 0"));
@ -1375,10 +1480,9 @@ vm_phys_alloc_queues_contig(
KASSERT(powerof2(boundary), ("boundary is not a power of 2")); KASSERT(powerof2(boundary), ("boundary is not a power of 2"));
/* Compute the queue that is the best fit for npages. */ /* Compute the queue that is the best fit for npages. */
order = flsl(npages - 1); order = flsl(npages - 1);
/* Search for a run satisfying the specified conditions. */ /* Search for a large enough free block. */
size = npages << PAGE_SHIFT; size = npages << PAGE_SHIFT;
for (oind = min(order, VM_NFREEORDER - 1); oind < VM_NFREEORDER; for (oind = order; oind < VM_NFREEORDER; oind++) {
oind++) {
for (pind = 0; pind < VM_NFREEPOOL; pind++) { for (pind = 0; pind < VM_NFREEPOOL; pind++) {
fl = (*queues)[pind]; fl = (*queues)[pind];
TAILQ_FOREACH(m_ret, &fl[oind].pl, listq) { TAILQ_FOREACH(m_ret, &fl[oind].pl, listq) {
@ -1390,74 +1494,24 @@ vm_phys_alloc_queues_contig(
*/ */
pa = VM_PAGE_TO_PHYS(m_ret); pa = VM_PAGE_TO_PHYS(m_ret);
pa_end = pa + size; pa_end = pa + size;
if (pa < low || pa_end > high || if (low <= pa && pa_end <= high &&
!vm_addr_ok(pa, size, alignment, boundary)) vm_addr_ok(pa, size, alignment, boundary))
continue; return (m_ret);
/*
* Is the size of this allocation request
* no more than the largest block size?
*/
if (order < VM_NFREEORDER)
goto done;
/*
* Determine if the address range is valid
* (without overflow in pa_end calculation)
* and fits within the segment.
*/
seg = &vm_phys_segs[m_ret->segind];
if (pa_end < pa || seg->end < pa_end)
continue;
/*
* Determine if a series of free oind-blocks
* starting here can satisfy the allocation
* request.
*/
do {
pa += 1 <<
(PAGE_SHIFT + VM_NFREEORDER - 1);
if (pa >= pa_end)
goto done;
} while (VM_NFREEORDER - 1 == seg->first_page[
atop(pa - seg->start)].order);
/*
* Determine if an additional series of free
* blocks of diminishing size can help to
* satisfy the allocation request.
*/
for (;;) {
m = &seg->first_page[
atop(pa - seg->start)];
if (m->order == VM_NFREEORDER ||
pa + (2 << (PAGE_SHIFT + m->order))
<= pa_end)
break;
pa += 1 << (PAGE_SHIFT + m->order);
if (pa >= pa_end)
goto done;
}
} }
} }
} }
if (order < VM_NFREEORDER)
return (NULL);
/* Search for a long-enough sequence of small blocks. */
oind = VM_NFREEORDER - 1;
for (pind = 0; pind < VM_NFREEPOOL; pind++) {
fl = (*queues)[pind];
m_ret = vm_phys_find_freelist_contig(fl, oind, npages,
low, high, alignment, boundary);
if (m_ret != NULL)
return (m_ret);
}
return (NULL); return (NULL);
done:
for (m = m_ret; m < &m_ret[npages]; m = &m[1 << oind]) {
fl = (*queues)[m->pool];
oind = m->order;
vm_freelist_rem(fl, m, oind);
if (m->pool != VM_FREEPOOL_DEFAULT)
vm_phys_set_pool(VM_FREEPOOL_DEFAULT, m, oind);
}
/* Return excess pages to the free lists. */
npages_end = roundup2(npages, 1 << oind);
if (npages < npages_end) {
fl = (*queues)[VM_FREEPOOL_DEFAULT];
vm_phys_enq_range(&m_ret[npages], npages_end - npages, fl, 0);
}
return (m_ret);
} }
/* /*
@ -1475,10 +1529,11 @@ vm_phys_alloc_contig(int domain, u_long npages, vm_paddr_t low, vm_paddr_t high,
u_long alignment, vm_paddr_t boundary) u_long alignment, vm_paddr_t boundary)
{ {
vm_paddr_t pa_end, pa_start; vm_paddr_t pa_end, pa_start;
vm_page_t m_run; struct vm_freelist *fl;
vm_page_t m, m_run;
struct vm_phys_seg *seg; struct vm_phys_seg *seg;
struct vm_freelist (*queues)[VM_NFREEPOOL][VM_NFREEORDER_MAX]; struct vm_freelist (*queues)[VM_NFREEPOOL][VM_NFREEORDER_MAX];
int segind; int oind, segind;
KASSERT(npages > 0, ("npages is 0")); KASSERT(npages > 0, ("npages is 0"));
KASSERT(powerof2(alignment), ("alignment is not a power of 2")); KASSERT(powerof2(alignment), ("alignment is not a power of 2"));
@ -1513,11 +1568,27 @@ vm_phys_alloc_contig(int domain, u_long npages, vm_paddr_t low, vm_paddr_t high,
if (seg->free_queues == queues) if (seg->free_queues == queues)
continue; continue;
queues = seg->free_queues; queues = seg->free_queues;
m_run = vm_phys_alloc_queues_contig(queues, npages, m_run = vm_phys_find_queues_contig(queues, npages,
low, high, alignment, boundary); low, high, alignment, boundary);
if (m_run != NULL) if (m_run != NULL)
break; break;
} }
if (m_run == NULL)
return (NULL);
/* Allocate pages from the page-range found. */
for (m = m_run; m < &m_run[npages]; m = &m[1 << oind]) {
fl = (*queues)[m->pool];
oind = m->order;
vm_freelist_rem(fl, m, oind);
if (m->pool != VM_FREEPOOL_DEFAULT)
vm_phys_set_pool(VM_FREEPOOL_DEFAULT, m, oind);
}
/* Return excess pages to the free lists. */
if (&m_run[npages] < m) {
fl = (*queues)[VM_FREEPOOL_DEFAULT];
vm_phys_enq_range(&m_run[npages], m - &m_run[npages], fl, 0);
}
return (m_run); return (m_run);
} }