Author: markj
Date: Wed Aug 21 16:11:12 2019
New Revision: 351333
URL: https://svnweb.freebsd.org/changeset/base/351333
Log:
Simplify vm_page_dequeue() and fix an assertion.
- Add a vm_pagequeue_remove() function to physically remove a page
from its queue and update the queue length.
- Remove vm_page_pagequeue_lockptr() and let vm_page_pagequeue()
return NULL for dequeued pages.
- Avoid unnecessarily reloading the queue index if vm_page_dequeue()
loses a race with a concurrent queue operation.
- Correct an always-true assertion: vm_page_dequeue() may be called
from the page allocator with the page unlocked. The assertion
m->order == VM_NFREEORDER simply tests whether the page has been
removed from the vm_phys free lists; instead, check whether the
page belongs to an object.
Reviewed by: kib
MFC after: 1 week
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21341
Modified:
head/sys/vm/vm_page.c
head/sys/vm/vm_page.h
head/sys/vm/vm_pagequeue.h
Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c Wed Aug 21 16:01:17 2019 (r351332)
+++ head/sys/vm/vm_page.c Wed Aug 21 16:11:12 2019 (r351333)
@@ -3056,21 +3056,15 @@ vm_waitpfault(struct domainset *dset, int timo)
mtx_unlock(&vm_domainset_lock);
}
-struct vm_pagequeue *
+static struct vm_pagequeue *
vm_page_pagequeue(vm_page_t m)
{
- return (&vm_pagequeue_domain(m)->vmd_pagequeues[m->queue]);
-}
-
-static struct mtx *
-vm_page_pagequeue_lockptr(vm_page_t m)
-{
uint8_t queue;
if ((queue = atomic_load_8(&m->queue)) == PQ_NONE)
return (NULL);
- return (&vm_pagequeue_domain(m)->vmd_pagequeues[queue].pq_mutex);
+ return (&vm_pagequeue_domain(m)->vmd_pagequeues[queue]);
}
static inline void
@@ -3093,10 +3087,8 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_pa
m, pq, qflags));
if ((qflags & PGA_DEQUEUE) != 0) {
- if (__predict_true((qflags & PGA_ENQUEUED) != 0)) {
- TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
- vm_pagequeue_cnt_dec(pq);
- }
+ if (__predict_true((qflags & PGA_ENQUEUED) != 0))
+ vm_pagequeue_remove(pq, m);
vm_page_dequeue_complete(m);
} else if ((qflags & (PGA_REQUEUE | PGA_REQUEUE_HEAD)) != 0) {
if ((qflags & PGA_ENQUEUED) != 0)
@@ -3299,16 +3291,14 @@ vm_page_dequeue_deferred_free(vm_page_t m)
void
vm_page_dequeue(vm_page_t m)
{
- struct mtx *lock, *lock1;
- struct vm_pagequeue *pq;
+ struct vm_pagequeue *pq, *pq1;
uint8_t aflags;
- KASSERT(mtx_owned(vm_page_lockptr(m)) || m->order == VM_NFREEORDER,
+ KASSERT(mtx_owned(vm_page_lockptr(m)) || m->object == NULL,
("page %p is allocated and unlocked", m));
- for (;;) {
- lock = vm_page_pagequeue_lockptr(m);
- if (lock == NULL) {
+ for (pq = vm_page_pagequeue(m);; pq = pq1) {
+ if (pq == NULL) {
/*
* A thread may be concurrently executing
* vm_page_dequeue_complete(). Ensure that all queue
@@ -3327,27 +3317,24 @@ vm_page_dequeue(vm_page_t m)
* critical section.
*/
cpu_spinwait();
+ pq1 = vm_page_pagequeue(m);
continue;
}
- mtx_lock(lock);
- if ((lock1 = vm_page_pagequeue_lockptr(m)) == lock)
+ vm_pagequeue_lock(pq);
+ if ((pq1 = vm_page_pagequeue(m)) == pq)
break;
- mtx_unlock(lock);
- lock = lock1;
+ vm_pagequeue_unlock(pq);
}
- KASSERT(lock == vm_page_pagequeue_lockptr(m),
+ KASSERT(pq == vm_page_pagequeue(m),
("%s: page %p migrated directly between queues", __func__, m));
KASSERT((m->aflags & PGA_DEQUEUE) != 0 ||
mtx_owned(vm_page_lockptr(m)),
("%s: queued unlocked page %p", __func__, m));
- if ((m->aflags & PGA_ENQUEUED) != 0) {
- pq = vm_page_pagequeue(m);
- TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
- vm_pagequeue_cnt_dec(pq);
- }
+ if ((m->aflags & PGA_ENQUEUED) != 0)
+ vm_pagequeue_remove(pq, m);
vm_page_dequeue_complete(m);
- mtx_unlock(lock);
+ vm_pagequeue_unlock(pq);
}
/*
Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h Wed Aug 21 16:01:17 2019 (r351332)
+++ head/sys/vm/vm_page.h Wed Aug 21 16:11:12 2019 (r351333)
@@ -552,7 +552,6 @@ void vm_page_launder(vm_page_t m);
vm_page_t vm_page_lookup (vm_object_t, vm_pindex_t);
vm_page_t vm_page_next(vm_page_t m);
int vm_page_pa_tryrelock(pmap_t, vm_paddr_t, vm_paddr_t *);
-struct vm_pagequeue *vm_page_pagequeue(vm_page_t m);
vm_page_t vm_page_prev(vm_page_t m);
bool vm_page_ps_test(vm_page_t m, int flags, vm_page_t skip_m);
void vm_page_putfake(vm_page_t m);
Modified: head/sys/vm/vm_pagequeue.h
==============================================================================
--- head/sys/vm/vm_pagequeue.h Wed Aug 21 16:01:17 2019 (r351332)
+++ head/sys/vm/vm_pagequeue.h Wed Aug 21 16:11:12 2019 (r351333)
@@ -199,6 +199,14 @@ vm_pagequeue_cnt_add(struct vm_pagequeue *pq, int adde
#define vm_pagequeue_cnt_dec(pq) vm_pagequeue_cnt_add((pq), -1)
static inline void
+vm_pagequeue_remove(struct vm_pagequeue *pq, vm_page_t m)
+{
+
+ TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
+ vm_pagequeue_cnt_dec(pq);
+}
+
+static inline void
vm_batchqueue_init(struct vm_batchqueue *bq)
{
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