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(5/6) Move the VPO_NOSYNC to PGA_NOSYNC to eliminate the dependency on the

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object lock in vm_page_set_validclean().

Reviewed by:    kib, markj
Tested by:      pho
Sponsored by:   Netflix, Intel
Differential Revision:	https://reviews.freebsd.org/D21595
This commit is contained in:
jeff 2019-10-15 03:48:22 +00:00
parent e249e932a5
commit 786dad5c20
5 changed files with 18 additions and 19 deletions
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13
sys/vm/vm_fault.c
View File

@ -225,15 +225,14 @@ vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
* FALSE, one for the map entry with MAP_ENTRY_NOSYNC
* flag set, other with flag clear, race, it is
* possible for the no-NOSYNC thread to see m->dirty
* != 0 and not clear VPO_NOSYNC. Take vm_page lock
* around manipulation of VPO_NOSYNC and
* vm_page_dirty() call, to avoid the race and keep
* m->oflags consistent.
* != 0 and not clear PGA_NOSYNC. Take vm_page lock
* around manipulation of PGA_NOSYNC and
* vm_page_dirty() call to avoid the race.
*/
vm_page_lock(m);
/*
* If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
* If this is a NOSYNC mmap we do not want to set PGA_NOSYNC
* if the page is already dirty to prevent data written with
* the expectation of being synced from not being synced.
* Likewise if this entry does not request NOSYNC then make
@ -242,10 +241,10 @@ vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
*/
if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
if (m->dirty == 0) {
m->oflags |= VPO_NOSYNC;
vm_page_aflag_set(m, PGA_NOSYNC);
}
} else {
m->oflags &= ~VPO_NOSYNC;
vm_page_aflag_clear(m, PGA_NOSYNC);
}
/*

7
sys/vm/vm_object.c
View File

@ -772,12 +772,14 @@ static boolean_t
vm_object_page_remove_write(vm_page_t p, int flags, boolean_t *clearobjflags)
{
vm_page_assert_busied(p);
/*
* If we have been asked to skip nosync pages and this is a
* nosync page, skip it. Note that the object flags were not
* cleared in this case so we do not have to set them.
*/
if ((flags & OBJPC_NOSYNC) != 0 && (p->oflags & VPO_NOSYNC) != 0) {
if ((flags & OBJPC_NOSYNC) != 0 && (p->aflags & PGA_NOSYNC) != 0) {
*clearobjflags = FALSE;
return (FALSE);
} else {
@ -791,7 +793,7 @@ vm_object_page_remove_write(vm_page_t p, int flags, boolean_t *clearobjflags)
*
* Clean all dirty pages in the specified range of object. Leaves page
* on whatever queue it is currently on. If NOSYNC is set then do not
* write out pages with VPO_NOSYNC set (originally comes from MAP_NOSYNC),
* write out pages with PGA_NOSYNC set (originally comes from MAP_NOSYNC),
* leaving the object dirty.
*
* When stuffing pages asynchronously, allow clustering. XXX we need a
@ -2270,7 +2272,6 @@ void
vm_object_unbusy(vm_object_t obj)
{
VM_OBJECT_ASSERT_LOCKED(obj);
refcount_release(&obj->busy);
}

2
sys/vm/vm_object.h
View File

@ -209,7 +209,7 @@ struct vm_object {
#define OBJPC_SYNC 0x1 /* sync I/O */
#define OBJPC_INVAL 0x2 /* invalidate */
#define OBJPC_NOSYNC 0x4 /* skip if VPO_NOSYNC */
#define OBJPC_NOSYNC 0x4 /* skip if PGA_NOSYNC */
/*
* The following options are supported by vm_object_page_remove().

11
sys/vm/vm_page.c
View File

@ -2506,7 +2506,7 @@ vm_page_scan_contig(u_long npages, vm_page_t m_start, vm_page_t m_end,
KASSERT((m->oflags & (VPO_SWAPINPROG |
VPO_SWAPSLEEP | VPO_UNMANAGED)) == 0,
("page %p has unexpected oflags", m));
/* Don't care: VPO_NOSYNC. */
/* Don't care: PGA_NOSYNC. */
run_ext = 1;
} else
run_ext = 0;
@ -2655,7 +2655,7 @@ vm_page_reclaim_run(int req_class, int domain, u_long npages, vm_page_t m_run,
KASSERT((m->oflags & (VPO_SWAPINPROG |
VPO_SWAPSLEEP | VPO_UNMANAGED)) == 0,
("page %p has unexpected oflags", m));
/* Don't care: VPO_NOSYNC. */
/* Don't care: PGA_NOSYNC. */
if (!vm_page_none_valid(m)) {
/*
* First, try to allocate a new page
@ -2721,7 +2721,6 @@ vm_page_reclaim_run(int req_class, int domain, u_long npages, vm_page_t m_run,
~PGA_QUEUE_STATE_MASK;
KASSERT(m_new->oflags == VPO_UNMANAGED,
("page %p is managed", m_new));
m_new->oflags = m->oflags & VPO_NOSYNC;
pmap_copy_page(m, m_new);
m_new->valid = m->valid;
m_new->dirty = m->dirty;
@ -4703,8 +4702,6 @@ vm_page_set_validclean(vm_page_t m, int base, int size)
vm_page_bits_t oldvalid, pagebits;
int endoff, frag;
/* Object lock for VPO_NOSYNC */
VM_OBJECT_ASSERT_WLOCKED(m->object);
vm_page_assert_busied(m);
if (size == 0) /* handle degenerate case */
return;
@ -4732,7 +4729,7 @@ vm_page_set_validclean(vm_page_t m, int base, int size)
/*
* Set valid, clear dirty bits. If validating the entire
* page we can safely clear the pmap modify bit. We also
* use this opportunity to clear the VPO_NOSYNC flag. If a process
* use this opportunity to clear the PGA_NOSYNC flag. If a process
* takes a write fault on a MAP_NOSYNC memory area the flag will
* be set again.
*
@ -4773,7 +4770,7 @@ vm_page_set_validclean(vm_page_t m, int base, int size)
*/
pmap_clear_modify(m);
m->dirty = 0;
m->oflags &= ~VPO_NOSYNC;
vm_page_aflag_clear(m, PGA_NOSYNC);
} else if (oldvalid != VM_PAGE_BITS_ALL && vm_page_xbusied(m))
m->dirty &= ~pagebits;
else

4
sys/vm/vm_page.h
View File

@ -287,7 +287,6 @@ struct vm_page {
#define VPO_SWAPSLEEP 0x02 /* waiting for swap to finish */
#define VPO_UNMANAGED 0x04 /* no PV management for page */
#define VPO_SWAPINPROG 0x08 /* swap I/O in progress on page */
#define VPO_NOSYNC 0x10 /* do not collect for syncer */
/*
* Busy page implementation details.
@ -390,6 +389,8 @@ extern struct mtx_padalign pa_lock[];
* PGA_EXECUTABLE may be set by pmap routines, and indicates that a page has
* at least one executable mapping. It is not consumed by the MI VM layer.
*
* PGA_NOSYNC must be set and cleared with the page busy lock held.
*
* PGA_ENQUEUED is set and cleared when a page is inserted into or removed
* from a page queue, respectively. It determines whether the plinks.q field
* of the page is valid. To set or clear this flag, the queue lock for the
@ -420,6 +421,7 @@ extern struct mtx_padalign pa_lock[];
#define PGA_DEQUEUE 0x10 /* page is due to be dequeued */
#define PGA_REQUEUE 0x20 /* page is due to be requeued */
#define PGA_REQUEUE_HEAD 0x40 /* page requeue should bypass LRU */
#define PGA_NOSYNC 0x80 /* do not collect for syncer */
#define PGA_QUEUE_STATE_MASK (PGA_ENQUEUED | PGA_DEQUEUE | PGA_REQUEUE | \
PGA_REQUEUE_HEAD)