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In vm_page_xunbusy_maybelocked(), add fast path for unbusy when no

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waiters exist, same as for vm_page_xunbusy().  If previous value of
busy_lock was VPB_SINGLE_EXCLUSIVER, no waiters existed and wakeup is
not needed.

Move common code from vm_page_xunbusy_maybelocked() and
vm_page_xunbusy_hard() to vm_page_xunbusy_locked().

Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Approved by:	re (gjb)
This commit is contained in:
Konstantin Belousov 2016-06-23 08:28:13 +00:00
parent 505cd5d13b
commit 35e8002c58
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=302131
1 changed files with 22 additions and 4 deletions
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26
sys/vm/vm_page.c
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@ -759,6 +759,18 @@ vm_page_trysbusy(vm_page_t m)
}
}
static void
vm_page_xunbusy_locked(vm_page_t m)
{
vm_page_assert_xbusied(m);
vm_page_assert_locked(m);
atomic_store_rel_int(&m->busy_lock, VPB_UNBUSIED);
/* There is a waiter, do wakeup() instead of vm_page_flash(). */
wakeup(m);
}
static void
vm_page_xunbusy_maybelocked(vm_page_t m)
{
@ -766,11 +778,18 @@ vm_page_xunbusy_maybelocked(vm_page_t m)
vm_page_assert_xbusied(m);
/*
* Fast path for unbusy. If it succeeds, we know that there
* are no waiters, so we do not need a wakeup.
*/
if (atomic_cmpset_rel_int(&m->busy_lock, VPB_SINGLE_EXCLUSIVER,
VPB_UNBUSIED))
return;
lockacq = !mtx_owned(vm_page_lockptr(m));
if (lockacq)
vm_page_lock(m);
vm_page_flash(m);
atomic_store_rel_int(&m->busy_lock, VPB_UNBUSIED);
vm_page_xunbusy_locked(m);
if (lockacq)
vm_page_unlock(m);
}
@ -788,8 +807,7 @@ vm_page_xunbusy_hard(vm_page_t m)
vm_page_assert_xbusied(m);
vm_page_lock(m);
atomic_store_rel_int(&m->busy_lock, VPB_UNBUSIED);
wakeup(m);
vm_page_xunbusy_locked(m);
vm_page_unlock(m);
}