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Significantly reduce the cost, i.e., run time, of calls to madvise(...,

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MADV_DONTNEED) and madvise(..., MADV_FREE).  Specifically, introduce a new
pmap function, pmap_advise(), that operates on a range of virtual addresses
within the specified pmap, allowing for a more efficient implementation of
MADV_DONTNEED and MADV_FREE.  Previously, the implementation of
MADV_DONTNEED and MADV_FREE relied on per-page pmap operations, such as
pmap_clear_reference().  Intuitively, the problem with this implementation
is that the pmap-level locks are acquired and released and the page table
traversed repeatedly, once for each resident page in the range
that was specified to madvise(2).  A more subtle flaw with the previous
implementation is that pmap_clear_reference() would clear the reference bit
on all mappings to the specified page, not just the mapping in the range
specified to madvise(2).

Since our malloc(3) makes heavy use of madvise(2), this change can have a
measureable impact.  For example, the system time for completing a parallel
"buildworld" on a 6-core amd64 machine was reduced by about 1.5% to 2.0%.

Note: This change only contains pmap_advise() implementations for a subset
of our supported architectures.  I will commit implementations for the
remaining architectures after further testing.  For now, a stub function is
sufficient because of the advisory nature of pmap_advise().

Discussed with: jeff, jhb, kib
Tested by:      pho (i386), marcel (ia64)
Sponsored by:   EMC / Isilon Storage Division
This commit is contained in:
Alan Cox 2013-08-29 15:49:05 +00:00
parent e733e239ee
commit 51321f7c31
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=255028
13 changed files with 419 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

122
sys/amd64/amd64/pmap.c
View File

@ -4966,6 +4966,128 @@ pmap_ts_referenced(vm_page_t m)
return (rtval);
}
/*
* Apply the given advice to the specified range of addresses within the
* given pmap. Depending on the advice, clear the referenced and/or
* modified flags in each mapping and set the mapped page's dirty field.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
struct rwlock *lock;
pml4_entry_t *pml4e;
pdp_entry_t *pdpe;
pd_entry_t oldpde, *pde;
pt_entry_t *pte;
vm_offset_t va_next;
vm_page_t m;
boolean_t anychanged, pv_lists_locked;
if (advice != MADV_DONTNEED && advice != MADV_FREE)
return;
pv_lists_locked = FALSE;
resume:
anychanged = FALSE;
PMAP_LOCK(pmap);
for (; sva < eva; sva = va_next) {
pml4e = pmap_pml4e(pmap, sva);
if ((*pml4e & PG_V) == 0) {
va_next = (sva + NBPML4) & ~PML4MASK;
if (va_next < sva)
va_next = eva;
continue;
}
pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
if ((*pdpe & PG_V) == 0) {
va_next = (sva + NBPDP) & ~PDPMASK;
if (va_next < sva)
va_next = eva;
continue;
}
va_next = (sva + NBPDR) & ~PDRMASK;
if (va_next < sva)
va_next = eva;
pde = pmap_pdpe_to_pde(pdpe, sva);
oldpde = *pde;
if ((oldpde & PG_V) == 0)
continue;
else if ((oldpde & PG_PS) != 0) {
if ((oldpde & PG_MANAGED) == 0)
continue;
if (!pv_lists_locked) {
pv_lists_locked = TRUE;
if (!rw_try_rlock(&pvh_global_lock)) {
if (anychanged)
pmap_invalidate_all(pmap);
PMAP_UNLOCK(pmap);
rw_rlock(&pvh_global_lock);
goto resume;
}
}
lock = NULL;
if (!pmap_demote_pde_locked(pmap, pde, sva, &lock)) {
if (lock != NULL)
rw_wunlock(lock);
/*
* The large page mapping was destroyed.
*/
continue;
}
/*
* Unless the page mappings are wired, remove the
* mapping to a single page so that a subsequent
* access may repromote. Since the underlying page
* table page is fully populated, this removal never
* frees a page table page.
*/
if ((oldpde & PG_W) == 0) {
pte = pmap_pde_to_pte(pde, sva);
KASSERT((*pte & PG_V) != 0,
("pmap_advise: invalid PTE"));
pmap_remove_pte(pmap, pte, sva, *pde, NULL,
&lock);
anychanged = TRUE;
}
if (lock != NULL)
rw_wunlock(lock);
}
if (va_next > eva)
va_next = eva;
for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
sva += PAGE_SIZE) {
if ((*pte & (PG_MANAGED | PG_V)) != (PG_MANAGED |
PG_V))
continue;
else if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
if (advice == MADV_DONTNEED) {
/*
* Future calls to pmap_is_modified()
* can be avoided by making the page
* dirty now.
*/
m = PHYS_TO_VM_PAGE(*pte & PG_FRAME);
vm_page_dirty(m);
}
atomic_clear_long(pte, PG_M | PG_A);
} else if ((*pte & PG_A) != 0)
atomic_clear_long(pte, PG_A);
else
continue;
if ((*pte & PG_G) != 0)
pmap_invalidate_page(pmap, sva);
else
anychanged = TRUE;
}
}
if (anychanged)
pmap_invalidate_all(pmap);
if (pv_lists_locked)
rw_runlock(&pvh_global_lock);
PMAP_UNLOCK(pmap);
}
/*
* Clear the modify bits on the specified physical page.
*/

8
sys/arm/arm/pmap-v6.c
View File

@ -4766,6 +4766,14 @@ pmap_is_modified(vm_page_t m)
return (rv);
}
/*
* This function is advisory.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
}
/*
* Clear the modify bits on the specified physical page.
*/

8
sys/arm/arm/pmap.c
View File

@ -4515,6 +4515,14 @@ pmap_page_wired_mappings(vm_page_t m)
return (count);
}
/*
* This function is advisory.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
}
/*
* pmap_ts_referenced:
*

106
sys/i386/i386/pmap.c
View File

@ -4833,6 +4833,112 @@ pmap_ts_referenced(vm_page_t m)
return (rtval);
}
/*
* Apply the given advice to the specified range of addresses within the
* given pmap. Depending on the advice, clear the referenced and/or
* modified flags in each mapping and set the mapped page's dirty field.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
pd_entry_t oldpde, *pde;
pt_entry_t *pte;
vm_offset_t pdnxt;
vm_page_t m;
boolean_t anychanged, pv_lists_locked;
if (advice != MADV_DONTNEED && advice != MADV_FREE)
return;
if (pmap_is_current(pmap))
pv_lists_locked = FALSE;
else {
pv_lists_locked = TRUE;
resume:
rw_wlock(&pvh_global_lock);
sched_pin();
}
anychanged = FALSE;
PMAP_LOCK(pmap);
for (; sva < eva; sva = pdnxt) {
pdnxt = (sva + NBPDR) & ~PDRMASK;
if (pdnxt < sva)
pdnxt = eva;
pde = pmap_pde(pmap, sva);
oldpde = *pde;
if ((oldpde & PG_V) == 0)
continue;
else if ((oldpde & PG_PS) != 0) {
if ((oldpde & PG_MANAGED) == 0)
continue;
if (!pv_lists_locked) {
pv_lists_locked = TRUE;
if (!rw_try_wlock(&pvh_global_lock)) {
if (anychanged)
pmap_invalidate_all(pmap);
PMAP_UNLOCK(pmap);
goto resume;
}
sched_pin();
}
if (!pmap_demote_pde(pmap, pde, sva)) {
/*
* The large page mapping was destroyed.
*/
continue;
}
/*
* Unless the page mappings are wired, remove the
* mapping to a single page so that a subsequent
* access may repromote. Since the underlying page
* table page is fully populated, this removal never
* frees a page table page.
*/
if ((oldpde & PG_W) == 0) {
pte = pmap_pte_quick(pmap, sva);
KASSERT((*pte & PG_V) != 0,
("pmap_advise: invalid PTE"));
pmap_remove_pte(pmap, pte, sva, NULL);
anychanged = TRUE;
}
}
if (pdnxt > eva)
pdnxt = eva;
for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++,
sva += PAGE_SIZE) {
if ((*pte & (PG_MANAGED | PG_V)) != (PG_MANAGED |
PG_V))
continue;
else if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
if (advice == MADV_DONTNEED) {
/*
* Future calls to pmap_is_modified()
* can be avoided by making the page
* dirty now.
*/
m = PHYS_TO_VM_PAGE(*pte & PG_FRAME);
vm_page_dirty(m);
}
atomic_clear_int((u_int *)pte, PG_M | PG_A);
} else if ((*pte & PG_A) != 0)
atomic_clear_int((u_int *)pte, PG_A);
else
continue;
if ((*pte & PG_G) != 0)
pmap_invalidate_page(pmap, sva);
else
anychanged = TRUE;
}
}
if (anychanged)
pmap_invalidate_all(pmap);
if (pv_lists_locked) {
sched_unpin();
rw_wunlock(&pvh_global_lock);
}
PMAP_UNLOCK(pmap);
}
/*
* Clear the modify bits on the specified physical page.
*/

66
sys/i386/xen/pmap.c
View File

@ -3913,6 +3913,72 @@ pmap_ts_referenced(vm_page_t m)
return (rtval);
}
/*
* Apply the given advice to the specified range of addresses within the
* given pmap. Depending on the advice, clear the referenced and/or
* modified flags in each mapping and set the mapped page's dirty field.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
pd_entry_t oldpde;
pt_entry_t *pte;
vm_offset_t pdnxt;
vm_page_t m;
boolean_t anychanged;
if (advice != MADV_DONTNEED && advice != MADV_FREE)
return;
anychanged = FALSE;
rw_wlock(&pvh_global_lock);
sched_pin();
PMAP_LOCK(pmap);
for (; sva < eva; sva = pdnxt) {
pdnxt = (sva + NBPDR) & ~PDRMASK;
if (pdnxt < sva)
pdnxt = eva;
oldpde = pmap->pm_pdir[sva >> PDRSHIFT];
if ((oldpde & (PG_PS | PG_V)) != PG_V)
continue;
if (pdnxt > eva)
pdnxt = eva;
for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++,
sva += PAGE_SIZE) {
if ((*pte & (PG_MANAGED | PG_V)) != (PG_MANAGED |
PG_V))
continue;
else if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
if (advice == MADV_DONTNEED) {
/*
* Future calls to pmap_is_modified()
* can be avoided by making the page
* dirty now.
*/
m = PHYS_TO_VM_PAGE(xpmap_mtop(*pte) &
PG_FRAME);
vm_page_dirty(m);
}
PT_SET_VA_MA(pte, *pte & ~(PG_M | PG_A), TRUE);
} else if ((*pte & PG_A) != 0)
PT_SET_VA_MA(pte, *pte & ~PG_A, TRUE);
else
continue;
if ((*pte & PG_G) != 0)
pmap_invalidate_page(pmap, sva);
else
anychanged = TRUE;
}
}
PT_UPDATES_FLUSH();
if (*PMAP1)
PT_SET_VA_MA(PMAP1, 0, TRUE);
if (anychanged)
pmap_invalidate_all(pmap);
sched_unpin();
rw_wunlock(&pvh_global_lock);
PMAP_UNLOCK(pmap);
}
/*
* Clear the modify bits on the specified physical page.
*/

44
sys/ia64/ia64/pmap.c
View File

@ -2309,6 +2309,50 @@ pmap_is_referenced(vm_page_t m)
return (rv);
}
/*
* Apply the given advice to the specified range of addresses within the
* given pmap. Depending on the advice, clear the referenced and/or
* modified flags in each mapping and set the mapped page's dirty field.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
struct ia64_lpte *pte;
pmap_t oldpmap;
vm_page_t m;
PMAP_LOCK(pmap);
oldpmap = pmap_switch(pmap);
for (; sva < eva; sva += PAGE_SIZE) {
/* If page is invalid, skip this page. */
pte = pmap_find_vhpt(sva);
if (pte == NULL)
continue;
/* If it isn't managed, skip it too. */
if (!pmap_managed(pte))
continue;
/* Clear its modified and referenced bits. */
if (pmap_dirty(pte)) {
if (advice == MADV_DONTNEED) {
/*
* Future calls to pmap_is_modified() can be
* avoided by making the page dirty now.
*/
m = PHYS_TO_VM_PAGE(pmap_ppn(pte));
vm_page_dirty(m);
}
pmap_clear_dirty(pte);
} else if (!pmap_accessed(pte))
continue;
pmap_clear_accessed(pte);
pmap_invalidate_page(sva);
}
pmap_switch(oldpmap);
PMAP_UNLOCK(pmap);
}
/*
* Clear the modify bits on the specified physical page.
*/

8
sys/mips/mips/pmap.c
View File

@ -2913,6 +2913,14 @@ pmap_is_prefaultable(pmap_t pmap, vm_offset_t addr)
return (rv);
}
/*
* This function is advisory.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
}
/*
* Clear the modify bits on the specified physical page.
*/

19
sys/powerpc/powerpc/mmu_if.m
View File

@ -132,6 +132,25 @@ CODE {
};
/**
* @brief Apply the given advice to the specified range of addresses within
* the given pmap. Depending on the advice, clear the referenced and/or
* modified flags in each mapping and set the mapped page's dirty field.
*
* @param _pmap physical map
* @param _start virtual range start
* @param _end virtual range end
* @param _advice advice to apply
*/
METHOD void advise {
mmu_t _mmu;
pmap_t _pmap;
vm_offset_t _start;
vm_offset_t _end;
int _advice;
};
/**
* @brief Change the wiring attribute for the page in the given physical
* map and virtual address.

9
sys/powerpc/powerpc/pmap_dispatch.c
View File

@ -90,6 +90,15 @@ RB_GENERATE(pvo_tree, pvo_entry, pvo_plink, pvo_vaddr_compare);
#endif
void
pmap_advise(pmap_t pmap, vm_offset_t start, vm_offset_t end, int advice)
{
CTR5(KTR_PMAP, "%s(%p, %#x, %#x, %d)", __func__, pmap, start, end,
advice);
MMU_ADVISE(mmu_obj, pmap, start, end, advice);
}
void
pmap_change_wiring(pmap_t pmap, vm_offset_t va, boolean_t wired)
{

8
sys/sparc64/sparc64/pmap.c
View File

@ -2126,6 +2126,14 @@ pmap_is_referenced(vm_page_t m)
return (rv);
}
/*
* This function is advisory.
*/
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
}
void
pmap_clear_modify(vm_page_t m)
{

2
sys/vm/pmap.h
View File

@ -98,6 +98,8 @@ struct thread;
extern vm_offset_t kernel_vm_end;
void pmap_activate(struct thread *td);
void pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva,
int advice);
void pmap_align_superpage(vm_object_t, vm_ooffset_t, vm_offset_t *,
vm_size_t);
void pmap_change_wiring(pmap_t, vm_offset_t, boolean_t);

21
sys/vm/vm_map.c
View File

@ -2125,7 +2125,7 @@ vm_map_madvise(
(current != &map->header) && (current->start < end);
current = current->next
) {
vm_offset_t useStart;
vm_offset_t useEnd, useStart;
if (current->eflags & MAP_ENTRY_IS_SUB_MAP)
continue;
@ -2133,17 +2133,34 @@ vm_map_madvise(
pstart = OFF_TO_IDX(current->offset);
pend = pstart + atop(current->end - current->start);
useStart = current->start;
useEnd = current->end;
if (current->start < start) {
pstart += atop(start - current->start);
useStart = start;
}
if (current->end > end)
if (current->end > end) {
pend -= atop(current->end - end);
useEnd = end;
}
if (pstart >= pend)
continue;
/*
* Perform the pmap_advise() before clearing
* PGA_REFERENCED in vm_page_advise(). Otherwise, a
* concurrent pmap operation, such as pmap_remove(),
* could clear a reference in the pmap and set
* PGA_REFERENCED on the page before the pmap_advise()
* had completed. Consequently, the page would appear
* referenced based upon an old reference that
* occurred before this pmap_advise() ran.
*/
if (behav == MADV_DONTNEED || behav == MADV_FREE)
pmap_advise(map->pmap, useStart, useEnd,
behav);
vm_object_madvise(current->object.vm_object, pstart,
pend, behav);
if (behav == MADV_WILLNEED) {

9
sys/vm/vm_page.c
View File

@ -2634,7 +2634,6 @@ vm_page_advise(vm_page_t m, int advice)
* But we do make the page is freeable as we can without
* actually taking the step of unmapping it.
*/
pmap_clear_modify(m);
m->dirty = 0;
m->act_count = 0;
} else if (advice != MADV_DONTNEED)
@ -2654,15 +2653,7 @@ vm_page_advise(vm_page_t m, int advice)
/*
* Clear any references to the page. Otherwise, the page daemon will
* immediately reactivate the page.
*
* Perform the pmap_clear_reference() first. Otherwise, a concurrent
* pmap operation, such as pmap_remove(), could clear a reference in
* the pmap and set PGA_REFERENCED on the page before the
* pmap_clear_reference() had completed. Consequently, the page would
* appear referenced based upon an old reference that occurred before
* this function ran.
*/
pmap_clear_reference(m);
vm_page_aflag_clear(m, PGA_REFERENCED);
if (advice != MADV_FREE && m->dirty == 0 && pmap_is_modified(m))