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During vm_page_cache()'s call to vm_radix_insert(), if vm_page_alloc() was

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called to allocate a new page of radix trie nodes, there could be a call to
vm_radix_remove() on the same trie (of PG_CACHED pages) as the in-progress
vm_radix_insert().  With the removal of PG_CACHED pages, we can simplify
vm_radix_insert() and vm_radix_remove() by removing the flags on the root of
the trie that were used to detect this case and the code for restarting
vm_radix_insert() when it happened.

Reviewed by:	kib, markj
Tested by:	pho
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D8664
This commit is contained in:
alc 2016-12-01 17:26:37 +00:00
parent f936ea3345
commit 93bd5b27d2
3 changed files with 2 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
sys/vm/_vm_radix.h
View File

@ -36,12 +36,8 @@
*/
struct vm_radix {
uintptr_t rt_root;
uint8_t rt_flags;
};
#define RT_INSERT_INPROG 0x01
#define RT_TRIE_MODIFIED 0x02
#ifdef _KERNEL
static __inline boolean_t

1
sys/vm/vm_object.c
View File

@ -205,7 +205,6 @@ vm_object_zinit(void *mem, int size, int flags)
object->type = OBJT_DEAD;
object->ref_count = 0;
object->rtree.rt_root = 0;
object->rtree.rt_flags = 0;
object->paging_in_progress = 0;
object->resident_page_count = 0;
object->shadow_count = 0;

57
sys/vm/vm_radix.c
View File

@ -341,8 +341,6 @@ vm_radix_insert(struct vm_radix *rtree, vm_page_t page)
index = page->pindex;
restart:
/*
* The owner of record for root is not really important because it
* will never be used.
@ -360,32 +358,10 @@ vm_radix_insert(struct vm_radix *rtree, vm_page_t page)
panic("%s: key %jx is already present",
__func__, (uintmax_t)index);
clev = vm_radix_keydiff(m->pindex, index);
/*
* During node allocation the trie that is being
* walked can be modified because of recursing radix
* trie operations.
* If this is the case, the recursing functions signal
* such situation and the insert operation must
* start from scratch again.
* The freed radix node will then be in the UMA
* caches very likely to avoid the same situation
* to happen.
*/
rtree->rt_flags |= RT_INSERT_INPROG;
tmp = vm_radix_node_get(vm_radix_trimkey(index,
clev + 1), 2, clev);
rtree->rt_flags &= ~RT_INSERT_INPROG;
if (tmp == NULL) {
rtree->rt_flags &= ~RT_TRIE_MODIFIED;
if (tmp == NULL)
return (ENOMEM);
}
if ((rtree->rt_flags & RT_TRIE_MODIFIED) != 0) {
rtree->rt_flags &= ~RT_TRIE_MODIFIED;
tmp->rn_count = 0;
vm_radix_node_put(tmp);
goto restart;
}
*parentp = tmp;
vm_radix_addpage(tmp, index, clev, page);
vm_radix_addpage(tmp, m->pindex, clev, m);
@ -409,21 +385,9 @@ vm_radix_insert(struct vm_radix *rtree, vm_page_t page)
*/
newind = rnode->rn_owner;
clev = vm_radix_keydiff(newind, index);
/* See the comments above. */
rtree->rt_flags |= RT_INSERT_INPROG;
tmp = vm_radix_node_get(vm_radix_trimkey(index, clev + 1), 2, clev);
rtree->rt_flags &= ~RT_INSERT_INPROG;
if (tmp == NULL) {
rtree->rt_flags &= ~RT_TRIE_MODIFIED;
if (tmp == NULL)
return (ENOMEM);
}
if ((rtree->rt_flags & RT_TRIE_MODIFIED) != 0) {
rtree->rt_flags &= ~RT_TRIE_MODIFIED;
tmp->rn_count = 0;
vm_radix_node_put(tmp);
goto restart;
}
*parentp = tmp;
vm_radix_addpage(tmp, index, clev, page);
slot = vm_radix_slot(newind, clev);
@ -708,20 +672,6 @@ vm_radix_remove(struct vm_radix *rtree, vm_pindex_t index)
vm_page_t m;
int i, slot;
/*
* Detect if a page is going to be removed from a trie which is
* already undergoing another trie operation.
* Right now this is only possible for vm_radix_remove() recursing
* into vm_radix_insert().
* If this is the case, the caller must be notified about this
* situation. It will also takecare to update the RT_TRIE_MODIFIED
* accordingly.
* The RT_TRIE_MODIFIED bit is set here because the remove operation
* will always succeed.
*/
if ((rtree->rt_flags & RT_INSERT_INPROG) != 0)
rtree->rt_flags |= RT_TRIE_MODIFIED;
rnode = vm_radix_getroot(rtree);
if (vm_radix_isleaf(rnode)) {
m = vm_radix_topage(rnode);
@ -776,9 +726,6 @@ vm_radix_reclaim_allnodes(struct vm_radix *rtree)
{
struct vm_radix_node *root;
KASSERT((rtree->rt_flags & RT_INSERT_INPROG) == 0,
("vm_radix_reclaim_allnodes: unexpected trie recursion"));
root = vm_radix_getroot(rtree);
if (root == NULL)
return;