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Make MADV_FREE work better. Specifically, it did not wait for

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the page to be unbusy, and it caused some algorithmic problems
as a result.  There were some other problems with it also, so
this is a general cleanup of the code.
Submitted by:	Douglas Crosher <dtc@scrooge.ee.swin.oz.au> and myself.
This commit is contained in:
John Dyson 1997-01-20 02:25:14 +00:00
parent bfd34a4a60
commit 6e20a16589
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=21881
1 changed files with 46 additions and 13 deletions
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59
sys/vm/vm_object.c
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@ -681,6 +681,8 @@ vm_object_pmap_remove(object, start, end)
if (p->pindex >= start && p->pindex < end)
vm_page_protect(p, VM_PROT_NONE);
}
if ((start == 0) && (object->size == end))
object->flags &= ~OBJ_WRITEABLE;
}
/*
@ -695,7 +697,9 @@ vm_object_madvise(object, pindex, count, advise)
int count;
int advise;
{
vm_pindex_t end;
int s;
vm_pindex_t end, tpindex;
vm_object_t tobject;
vm_page_t m;
if (object == NULL)
@ -704,34 +708,60 @@ vm_object_madvise(object, pindex, count, advise)
end = pindex + count;
for (; pindex < end; pindex += 1) {
m = vm_page_lookup(object, pindex);
relookup:
tobject = object;
tpindex = pindex;
shadowlookup:
m = vm_page_lookup(tobject, tpindex);
if (m == NULL) {
if (tobject->type != OBJT_DEFAULT) {
continue;
}
tobject = tobject->backing_object;
if ((tobject == NULL) || (tobject->ref_count != 1)) {
continue;
}
tpindex += OFF_TO_IDX(tobject->backing_object_offset);
goto shadowlookup;
}
/*
* If the page is busy or not in a normal active state,
* we skip it. Things can break if we mess with pages
* in any of the below states.
*/
if (m == NULL || m->busy || (m->flags & PG_BUSY) ||
m->hold_count || m->wire_count ||
m->valid != VM_PAGE_BITS_ALL)
if (m->hold_count || m->wire_count ||
m->valid != VM_PAGE_BITS_ALL) {
continue;
}
if (m->busy || (m->flags & PG_BUSY)) {
s = splvm();
if (m->busy || (m->flags & PG_BUSY)) {
m->flags |= PG_WANTED;
tsleep(m, PVM, "madvpw", 0);
}
splx(s);
goto relookup;
}
if (advise == MADV_WILLNEED) {
if (m->queue != PQ_ACTIVE)
vm_page_activate(m);
} else if ((advise == MADV_DONTNEED) ||
((advise == MADV_FREE) &&
((object->type != OBJT_DEFAULT) &&
(object->type != OBJT_SWAP)))) {
} else if (advise == MADV_DONTNEED) {
vm_page_deactivate(m);
} else if (advise == MADV_FREE) {
pmap_clear_modify(VM_PAGE_TO_PHYS(m));
m->dirty = 0;
/*
* Force a demand-zero on next ref
* Force a demand zero if attempt to read from swap.
* We currently don't handle vnode files correctly,
* and will reread stale contents unnecessarily.
*/
if (object->type == OBJT_SWAP)
swap_pager_dmzspace(object, m->pindex, 1);
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
swap_pager_dmzspace(tobject, m->pindex, 1);
}
}
}
@ -853,6 +883,7 @@ vm_object_qcollapse(object)
swap_pager_freespace(backing_object,
backing_object_paging_offset_index + p->pindex, 1);
vm_page_rename(p, object, new_pindex);
vm_page_protect(p, VM_PROT_NONE);
p->dirty = VM_PAGE_BITS_ALL;
}
}
@ -968,7 +999,9 @@ vm_object_collapse(object)
PAGE_WAKEUP(p);
vm_page_free(p);
} else {
vm_page_protect(p, VM_PROT_NONE);
vm_page_rename(p, object, new_pindex);
p->dirty = VM_PAGE_BITS_ALL;
}
}
}