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Improve get_pv_entry()'s handling of low-memory conditions. After page

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allocation fails and pv entries are reclaimed, there may be an unused pv
entry in a pv chunk that survived the reclamation.  However, previously,
after reclamation, get_pv_entry() did not look for an unused pv entry in
a surviving pv chunk; it simply retried the page allocation.  Now, it
does look for an unused pv entry before retrying the page allocation.

Note: This only applies to RELENG_7.  Earlier branches use a different
pv entry allocator.

MFC after: 6 weeks
This commit is contained in:
Alan Cox 2007-11-30 07:14:42 +00:00
parent 666fd6f59e
commit 58041e4b9c
2 changed files with 35 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
sys/amd64/amd64/pmap.c
View File

@ -1747,6 +1747,7 @@ get_pv_entry(pmap_t pmap, int try)
static const struct timeval printinterval = { 60, 0 };
static struct timeval lastprint;
static vm_pindex_t colour;
struct vpgqueues *pq;
int bit, field;
pv_entry_t pv;
struct pv_chunk *pc;
@ -1761,6 +1762,8 @@ get_pv_entry(pmap_t pmap, int try)
printf("Approaching the limit on PV entries, consider "
"increasing either the vm.pmap.shpgperproc or the "
"vm.pmap.pv_entry_max sysctl.\n");
pq = NULL;
retry:
pc = TAILQ_FIRST(&pmap->pm_pvchunk);
if (pc != NULL) {
for (field = 0; field < _NPCM; field++) {
@ -1783,7 +1786,8 @@ get_pv_entry(pmap_t pmap, int try)
}
}
/* No free items, allocate another chunk */
m = vm_page_alloc(NULL, colour, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
m = vm_page_alloc(NULL, colour, (pq == &vm_page_queues[PQ_ACTIVE] ?
VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL) | VM_ALLOC_NOOBJ |
VM_ALLOC_WIRED);
if (m == NULL) {
if (try) {
@ -1796,18 +1800,16 @@ get_pv_entry(pmap_t pmap, int try)
* pages. After that, if a pv chunk entry is still needed,
* destroy mappings to active pages.
*/
PV_STAT(pmap_collect_inactive++);
pmap_collect(pmap, &vm_page_queues[PQ_INACTIVE]);
m = vm_page_alloc(NULL, colour,
VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED);
if (m == NULL) {
if (pq == NULL) {
PV_STAT(pmap_collect_inactive++);
pq = &vm_page_queues[PQ_INACTIVE];
} else if (pq == &vm_page_queues[PQ_INACTIVE]) {
PV_STAT(pmap_collect_active++);
pmap_collect(pmap, &vm_page_queues[PQ_ACTIVE]);
m = vm_page_alloc(NULL, colour,
VM_ALLOC_SYSTEM | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED);
if (m == NULL)
panic("get_pv_entry: increase vm.pmap.shpgperproc");
}
pq = &vm_page_queues[PQ_ACTIVE];
} else
panic("get_pv_entry: increase vm.pmap.shpgperproc");
pmap_collect(pmap, pq);
goto retry;
}
PV_STAT(pc_chunk_count++);
PV_STAT(pc_chunk_allocs++);

52
sys/i386/i386/pmap.c
View File

@ -1813,6 +1813,7 @@ get_pv_entry(pmap_t pmap, int try)
static const struct timeval printinterval = { 60, 0 };
static struct timeval lastprint;
static vm_pindex_t colour;
struct vpgqueues *pq;
int bit, field;
pv_entry_t pv;
struct pv_chunk *pc;
@ -1827,6 +1828,8 @@ get_pv_entry(pmap_t pmap, int try)
printf("Approaching the limit on PV entries, consider "
"increasing either the vm.pmap.shpgperproc or the "
"vm.pmap.pv_entry_max tunable.\n");
pq = NULL;
retry:
pc = TAILQ_FIRST(&pmap->pm_pvchunk);
if (pc != NULL) {
for (field = 0; field < _NPCM; field++) {
@ -1850,21 +1853,17 @@ get_pv_entry(pmap_t pmap, int try)
return (pv);
}
}
pc = (struct pv_chunk *)pmap_ptelist_alloc(&pv_vafree);
m = vm_page_alloc(NULL, colour, VM_ALLOC_NORMAL |
VM_ALLOC_NOOBJ | VM_ALLOC_WIRED);
if (m == NULL || pc == NULL) {
/*
* Access to the ptelist "pv_vafree" is synchronized by the page
* queues lock. If "pv_vafree" is currently non-empty, it will
* remain non-empty until pmap_ptelist_alloc() completes.
*/
if (pv_vafree == 0 || (m = vm_page_alloc(NULL, colour, (pq ==
&vm_page_queues[PQ_ACTIVE] ? VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL) |
VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
if (try) {
pv_entry_count--;
PV_STAT(pc_chunk_tryfail++);
if (m) {
vm_page_lock_queues();
vm_page_unwire(m, 0);
vm_page_free(m);
vm_page_unlock_queues();
}
if (pc)
pmap_ptelist_free(&pv_vafree, (vm_offset_t)pc);
return (NULL);
}
/*
@ -1872,30 +1871,21 @@ get_pv_entry(pmap_t pmap, int try)
* inactive pages. After that, if a pv chunk entry
* is still needed, destroy mappings to active pages.
*/
PV_STAT(pmap_collect_inactive++);
pmap_collect(pmap, &vm_page_queues[PQ_INACTIVE]);
if (m == NULL)
m = vm_page_alloc(NULL, colour, VM_ALLOC_NORMAL |
VM_ALLOC_NOOBJ | VM_ALLOC_WIRED);
if (pc == NULL)
pc = (struct pv_chunk *)pmap_ptelist_alloc(&pv_vafree);
if (m == NULL || pc == NULL) {
if (pq == NULL) {
PV_STAT(pmap_collect_inactive++);
pq = &vm_page_queues[PQ_INACTIVE];
} else if (pq == &vm_page_queues[PQ_INACTIVE]) {
PV_STAT(pmap_collect_active++);
pmap_collect(pmap, &vm_page_queues[PQ_ACTIVE]);
if (m == NULL)
m = vm_page_alloc(NULL, colour,
VM_ALLOC_SYSTEM | VM_ALLOC_NOOBJ |
VM_ALLOC_WIRED);
if (pc == NULL)
pc = (struct pv_chunk *)
pmap_ptelist_alloc(&pv_vafree);
if (m == NULL || pc == NULL)
panic("get_pv_entry: increase vm.pmap.shpgperproc");
}
pq = &vm_page_queues[PQ_ACTIVE];
} else
panic("get_pv_entry: increase vm.pmap.shpgperproc");
pmap_collect(pmap, pq);
goto retry;
}
PV_STAT(pc_chunk_count++);
PV_STAT(pc_chunk_allocs++);
colour++;
pc = (struct pv_chunk *)pmap_ptelist_alloc(&pv_vafree);
pmap_qenter((vm_offset_t)pc, &m, 1);
pc->pc_pmap = pmap;
pc->pc_map[0] = pc_freemask[0] & ~1ul; /* preallocated bit 0 */