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Refactor _vm_page_busy_sleep to reduce the delta between the various

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sleep routines and introduce a variant that supports lockless sleep.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D23612
This commit is contained in:
jeff 2020-02-17 01:08:00 +00:00
parent 75a1861990
commit 02694321f8
2 changed files with 75 additions and 29 deletions
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102
sys/vm/vm_page.c
View File

@ -174,7 +174,7 @@ static uma_zone_t fakepg_zone;
static void vm_page_alloc_check(vm_page_t m);
static bool _vm_page_busy_sleep(vm_object_t obj, vm_page_t m,
const char *wmesg, bool nonshared, bool locked);
vm_pindex_t pindex, const char *wmesg, int allocflags, bool locked);
static void vm_page_clear_dirty_mask(vm_page_t m, vm_page_bits_t pagebits);
static void vm_page_enqueue(vm_page_t m, uint8_t queue);
static bool vm_page_free_prep(vm_page_t m);
@ -846,7 +846,8 @@ vm_page_acquire_flags(vm_page_t m, int allocflags)
/*
* vm_page_busy_sleep_flags
*
* Sleep for busy according to VM_ALLOC_ parameters.
* Sleep for busy according to VM_ALLOC_ parameters. Returns true
* if the caller should retry and false otherwise.
*/
static bool
vm_page_busy_sleep_flags(vm_object_t object, vm_page_t m, const char *wmesg,
@ -855,18 +856,19 @@ vm_page_busy_sleep_flags(vm_object_t object, vm_page_t m, const char *wmesg,
if ((allocflags & VM_ALLOC_NOWAIT) != 0)
return (false);
/*
* Reference the page before unlocking and
* sleeping so that the page daemon is less
* likely to reclaim it.
* Reference the page before unlocking and sleeping so that
* the page daemon is less likely to reclaim it.
*/
if ((allocflags & VM_ALLOC_NOCREAT) == 0)
vm_page_aflag_set(m, PGA_REFERENCED);
if (_vm_page_busy_sleep(object, m, wmesg, (allocflags &
VM_ALLOC_IGN_SBUSY) != 0, true))
vm_page_reference(m);
if (_vm_page_busy_sleep(object, m, m->pindex, wmesg, allocflags, true))
VM_OBJECT_WLOCK(object);
if ((allocflags & VM_ALLOC_WAITFAIL) != 0)
return (false);
return (true);
}
@ -900,8 +902,8 @@ vm_page_busy_acquire(vm_page_t m, int allocflags)
else
locked = false;
MPASS(locked || vm_page_wired(m));
if (_vm_page_busy_sleep(obj, m, "vmpba",
(allocflags & VM_ALLOC_SBUSY) != 0, locked))
if (_vm_page_busy_sleep(obj, m, m->pindex, "vmpba", allocflags,
locked) && locked)
VM_OBJECT_WLOCK(obj);
if ((allocflags & VM_ALLOC_WAITFAIL) != 0)
return (false);
@ -1026,19 +1028,49 @@ vm_page_busy_sleep(vm_page_t m, const char *wmesg, bool nonshared)
VM_OBJECT_ASSERT_LOCKED(obj);
vm_page_lock_assert(m, MA_NOTOWNED);
if (!_vm_page_busy_sleep(obj, m, wmesg, nonshared, true))
if (!_vm_page_busy_sleep(obj, m, m->pindex, wmesg,
nonshared ? VM_ALLOC_SBUSY : 0 , true))
VM_OBJECT_DROP(obj);
}
/*
* vm_page_busy_sleep_unlocked:
*
* Sleep if the page is busy, using the page pointer as wchan.
* This is used to implement the hard-path of busying mechanism.
*
* If nonshared is true, sleep only if the page is xbusy.
*
* The object lock must not be held on entry. The operation will
* return if the page changes identity.
*/
void
vm_page_busy_sleep_unlocked(vm_object_t obj, vm_page_t m, vm_pindex_t pindex,
const char *wmesg, bool nonshared)
{
VM_OBJECT_ASSERT_UNLOCKED(obj);
vm_page_lock_assert(m, MA_NOTOWNED);
_vm_page_busy_sleep(obj, m, pindex, wmesg,
nonshared ? VM_ALLOC_SBUSY : 0, false);
}
/*
* _vm_page_busy_sleep:
*
* Internal busy sleep function.
* Internal busy sleep function. Verifies the page identity and
* lockstate against parameters. Returns true if it sleeps and
* false otherwise.
*
* If locked is true the lock will be dropped for any true returns
* and held for any false returns.
*/
static bool
_vm_page_busy_sleep(vm_object_t obj, vm_page_t m, const char *wmesg,
bool nonshared, bool locked)
_vm_page_busy_sleep(vm_object_t obj, vm_page_t m, vm_pindex_t pindex,
const char *wmesg, int allocflags, bool locked)
{
bool xsleep;
u_int x;
/*
@ -1049,23 +1081,36 @@ _vm_page_busy_sleep(vm_object_t obj, vm_page_t m, const char *wmesg,
if (locked)
VM_OBJECT_DROP(obj);
vm_object_busy_wait(obj, wmesg);
return (locked);
return (true);
}
sleepq_lock(m);
x = m->busy_lock;
if (x == VPB_UNBUSIED || (nonshared && (x & VPB_BIT_SHARED) != 0) ||
((x & VPB_BIT_WAITERS) == 0 &&
!atomic_cmpset_int(&m->busy_lock, x, x | VPB_BIT_WAITERS))) {
sleepq_release(m);
if (!vm_page_busied(m))
return (false);
}
xsleep = (allocflags & (VM_ALLOC_SBUSY | VM_ALLOC_IGN_SBUSY)) != 0;
sleepq_lock(m);
x = atomic_load_int(&m->busy_lock);
do {
/*
* If the page changes objects or becomes unlocked we can
* simply return.
*/
if (x == VPB_UNBUSIED ||
(xsleep && (x & VPB_BIT_SHARED) != 0) ||
m->object != obj || m->pindex != pindex) {
sleepq_release(m);
return (false);
}
if ((x & VPB_BIT_WAITERS) != 0)
break;
} while (!atomic_fcmpset_int(&m->busy_lock, &x, x | VPB_BIT_WAITERS));
if (locked)
VM_OBJECT_DROP(obj);
DROP_GIANT();
sleepq_add(m, NULL, wmesg, 0, 0);
sleepq_wait(m, PVM);
PICKUP_GIANT();
return (locked);
return (true);
}
/*
@ -1343,7 +1388,7 @@ vm_page_readahead_finish(vm_page_t m)
* be locked.
*/
int
vm_page_sleep_if_busy(vm_page_t m, const char *msg)
vm_page_sleep_if_busy(vm_page_t m, const char *wmesg)
{
vm_object_t obj;
@ -1358,8 +1403,7 @@ vm_page_sleep_if_busy(vm_page_t m, const char *msg)
* held by the callers.
*/
obj = m->object;
if (vm_page_busied(m) || (obj != NULL && obj->busy)) {
vm_page_busy_sleep(m, msg, false);
if (_vm_page_busy_sleep(obj, m, m->pindex, wmesg, 0, true)) {
VM_OBJECT_WLOCK(obj);
return (TRUE);
}
@ -1376,7 +1420,7 @@ vm_page_sleep_if_busy(vm_page_t m, const char *msg)
* be locked.
*/
int
vm_page_sleep_if_xbusy(vm_page_t m, const char *msg)
vm_page_sleep_if_xbusy(vm_page_t m, const char *wmesg)
{
vm_object_t obj;
@ -1391,8 +1435,8 @@ vm_page_sleep_if_xbusy(vm_page_t m, const char *msg)
* held by the callers.
*/
obj = m->object;
if (vm_page_xbusied(m) || (obj != NULL && obj->busy)) {
vm_page_busy_sleep(m, msg, true);
if (_vm_page_busy_sleep(obj, m, m->pindex, wmesg, VM_ALLOC_SBUSY,
true)) {
VM_OBJECT_WLOCK(obj);
return (TRUE);
}

2
sys/vm/vm_page.h
View File

@ -591,6 +591,8 @@ bool vm_page_busy_acquire(vm_page_t m, int allocflags);
void vm_page_busy_downgrade(vm_page_t m);
int vm_page_busy_tryupgrade(vm_page_t m);
void vm_page_busy_sleep(vm_page_t m, const char *msg, bool nonshared);
void vm_page_busy_sleep_unlocked(vm_object_t obj, vm_page_t m,
vm_pindex_t pindex, const char *wmesg, bool nonshared);
void vm_page_free(vm_page_t m);
void vm_page_free_zero(vm_page_t m);