svn commit: r357374 - head/sys/vm
Mark Johnston
markj at FreeBSD.org
Sat Feb 1 18:23:51 UTC 2020
Author: markj
Date: Sat Feb 1 18:23:51 2020
New Revision: 357374
URL: https://svnweb.freebsd.org/changeset/base/357374
Log:
Remove a couple of lingering usages of the page lock.
Update vm_page_scan_contig() and vm_page_reclaim_run() to stop using
vm_page_change_lock(). It has no use after r356157. Remove
vm_page_change_lock() now that it has no users.
Remove an unncessary check for wirings in vm_page_scan_contig(), which
was previously checking twice. The check is racy until
vm_page_reclaim_run() ensures that the page is unmapped, so one check is
sufficient.
Reviewed by: jeff, kib (previous versions)
Tested by: pho (previous version)
Differential Revision: https://reviews.freebsd.org/D23279
Modified:
head/sys/vm/vm_page.c
head/sys/vm/vm_page.h
Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c Sat Feb 1 17:54:46 2020 (r357373)
+++ head/sys/vm/vm_page.c Sat Feb 1 18:23:51 2020 (r357374)
@@ -1156,23 +1156,6 @@ vm_page_xunbusy_hard_unchecked(vm_page_t m)
}
/*
- * Avoid releasing and reacquiring the same page lock.
- */
-void
-vm_page_change_lock(vm_page_t m, struct mtx **mtx)
-{
- struct mtx *mtx1;
-
- mtx1 = vm_page_lockptr(m);
- if (*mtx == mtx1)
- return;
- if (*mtx != NULL)
- mtx_unlock(*mtx);
- *mtx = mtx1;
- mtx_lock(mtx1);
-}
-
-/*
* vm_page_unhold_pages:
*
* Unhold each of the pages that is referenced by the given array.
@@ -2444,7 +2427,6 @@ vm_page_t
vm_page_scan_contig(u_long npages, vm_page_t m_start, vm_page_t m_end,
u_long alignment, vm_paddr_t boundary, int options)
{
- struct mtx *m_mtx;
vm_object_t object;
vm_paddr_t pa;
vm_page_t m, m_run;
@@ -2458,7 +2440,6 @@ vm_page_scan_contig(u_long npages, vm_page_t m_start,
KASSERT(powerof2(boundary), ("boundary is not a power of 2"));
m_run = NULL;
run_len = 0;
- m_mtx = NULL;
for (m = m_start; m < m_end && run_len < npages; m += m_inc) {
KASSERT((m->flags & PG_MARKER) == 0,
("page %p is PG_MARKER", m));
@@ -2489,9 +2470,8 @@ vm_page_scan_contig(u_long npages, vm_page_t m_start,
} else
KASSERT(m_run != NULL, ("m_run == NULL"));
- vm_page_change_lock(m, &m_mtx);
- m_inc = 1;
retry:
+ m_inc = 1;
if (vm_page_wired(m))
run_ext = 0;
#if VM_NRESERVLEVEL > 0
@@ -2504,23 +2484,17 @@ retry:
pa);
}
#endif
- else if ((object = m->object) != NULL) {
+ else if ((object =
+ (vm_object_t)atomic_load_ptr(&m->object)) != NULL) {
/*
* The page is considered eligible for relocation if
* and only if it could be laundered or reclaimed by
* the page daemon.
*/
- if (!VM_OBJECT_TRYRLOCK(object)) {
- mtx_unlock(m_mtx);
- VM_OBJECT_RLOCK(object);
- mtx_lock(m_mtx);
- if (m->object != object) {
- /*
- * The page may have been freed.
- */
- VM_OBJECT_RUNLOCK(object);
- goto retry;
- }
+ VM_OBJECT_RLOCK(object);
+ if (object != m->object) {
+ VM_OBJECT_RUNLOCK(object);
+ goto retry;
}
/* Don't care: PG_NODUMP, PG_ZERO. */
if (object->type != OBJT_DEFAULT &&
@@ -2537,8 +2511,7 @@ retry:
vm_reserv_size(level)) - pa);
#endif
} else if (object->memattr == VM_MEMATTR_DEFAULT &&
- vm_page_queue(m) != PQ_NONE && !vm_page_busied(m) &&
- !vm_page_wired(m)) {
+ vm_page_queue(m) != PQ_NONE && !vm_page_busied(m)) {
/*
* The page is allocated but eligible for
* relocation. Extend the current run by one
@@ -2605,8 +2578,6 @@ retry:
}
}
}
- if (m_mtx != NULL)
- mtx_unlock(m_mtx);
if (run_len >= npages)
return (m_run);
return (NULL);
@@ -2634,7 +2605,6 @@ vm_page_reclaim_run(int req_class, int domain, u_long
vm_paddr_t high)
{
struct vm_domain *vmd;
- struct mtx *m_mtx;
struct spglist free;
vm_object_t object;
vm_paddr_t pa;
@@ -2647,42 +2617,28 @@ vm_page_reclaim_run(int req_class, int domain, u_long
error = 0;
m = m_run;
m_end = m_run + npages;
- m_mtx = NULL;
for (; error == 0 && m < m_end; m++) {
KASSERT((m->flags & (PG_FICTITIOUS | PG_MARKER)) == 0,
("page %p is PG_FICTITIOUS or PG_MARKER", m));
/*
- * Avoid releasing and reacquiring the same page lock.
+ * Racily check for wirings. Races are handled once the object
+ * lock is held and the page is unmapped.
*/
- vm_page_change_lock(m, &m_mtx);
-retry:
- /*
- * Racily check for wirings. Races are handled below.
- */
if (vm_page_wired(m))
error = EBUSY;
- else if ((object = m->object) != NULL) {
+ else if ((object =
+ (vm_object_t)atomic_load_ptr(&m->object)) != NULL) {
/*
* The page is relocated if and only if it could be
* laundered or reclaimed by the page daemon.
*/
- if (!VM_OBJECT_TRYWLOCK(object)) {
- mtx_unlock(m_mtx);
- VM_OBJECT_WLOCK(object);
- mtx_lock(m_mtx);
- if (m->object != object) {
- /*
- * The page may have been freed.
- */
- VM_OBJECT_WUNLOCK(object);
- goto retry;
- }
- }
+ VM_OBJECT_WLOCK(object);
/* Don't care: PG_NODUMP, PG_ZERO. */
- if (object->type != OBJT_DEFAULT &&
+ if (m->object != object ||
+ (object->type != OBJT_DEFAULT &&
object->type != OBJT_SWAP &&
- object->type != OBJT_VNODE)
+ object->type != OBJT_VNODE))
error = EINVAL;
else if (object->memattr != VM_MEMATTR_DEFAULT)
error = EINVAL;
@@ -2781,7 +2737,6 @@ retry:
* The new page must be deactivated
* before the object is unlocked.
*/
- vm_page_change_lock(m_new, &m_mtx);
vm_page_deactivate(m_new);
} else {
m->flags &= ~PG_ZERO;
@@ -2821,8 +2776,6 @@ unlock:
error = EINVAL;
}
}
- if (m_mtx != NULL)
- mtx_unlock(m_mtx);
if ((m = SLIST_FIRST(&free)) != NULL) {
int cnt;
Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h Sat Feb 1 17:54:46 2020 (r357373)
+++ head/sys/vm/vm_page.h Sat Feb 1 18:23:51 2020 (r357374)
@@ -609,7 +609,6 @@ vm_page_t vm_page_alloc_freelist(int, int);
vm_page_t vm_page_alloc_freelist_domain(int, int, int);
void vm_page_bits_set(vm_page_t m, vm_page_bits_t *bits, vm_page_bits_t set);
bool vm_page_blacklist_add(vm_paddr_t pa, bool verbose);
-void vm_page_change_lock(vm_page_t m, struct mtx **mtx);
vm_page_t vm_page_grab (vm_object_t, vm_pindex_t, int);
int vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
vm_page_t *ma, int count);
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