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Switching from a global hash table to per-vm_object radix tries for mapping

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vm_object page indices to on-disk swap space (r322913) has changed the
synchronization requirements for a couple swap pager functions.  Whereas
before a read lock on the vm object sufficed because of the global mutex
on the hash table, a write lock on the vm object may now be required.  In
particular, calls to vm_pager_page_unswapped() now require a write lock on
the vm_object.  Consequently, vm_fault()'s fast path cannot call
vm_pager_page_unswapped().  The swap space will have to be released at a
later point.

Reviewed by:	kib, markj
X-MFC with:	r322913
Differential Revision:	https://reviews.freebsd.org/D12134
This commit is contained in:
Alan Cox 2017-08-28 16:55:43 +00:00
parent f7ca2bbe44
commit d5efa0a475
1 changed files with 4 additions and 3 deletions
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7
sys/vm/vm_fault.c
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@ -236,14 +236,15 @@ vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
* written NOW so dirty it explicitly to save on
* pmap_is_modified() calls later.
*
* Also tell the backing pager, if any, that it should remove
* any swap backing since the page is now dirty.
* Also, since the page is now dirty, we can possibly tell
* the pager to release any swap backing the page. Calling
* the pager requires a write lock on the object.
*/
if (need_dirty)
vm_page_dirty(m);
if (!set_wd)
vm_page_unlock(m);
if (need_dirty)
else if (need_dirty)
vm_pager_page_unswapped(m);
}