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Don't update per-page activation counts in the swapout code.

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This avoids duplicating the work of the page daemon's active queue scan.
Moreover, this duplication was inconsistent:
- PGA_REFERENCED is not counted in act_count unless pmap_ts_referenced()
  returned 0, but the page daemon always counts PGA_REFERENCED towards
  the activation count.
- The swapout daemon always activates a referenced page, but the page
  daemon only does so when the containing object is mapped at least
  once.

The main purpose of swapout_deactivate_pages() is to shrink the number
of pages mapped into a given pmap.  To do this without unmapping active
pages, use the non-destructive pmap_is_referenced() instead of the
destructive pmap_ts_referenced() and deactivate pages accordingly.
This simplifies some future changes to the locking protocol for page
queue state.

Reviewed by:	kib
Discussed with:	jeff
Tested by:	pho
Sponsored by:	Netflix, Intel
Differential Revision:	https://reviews.freebsd.org/D22674
This commit is contained in:
markj 2019-12-28 19:03:17 +00:00
parent 56bbe48921
commit d6943b904b
1 changed files with 12 additions and 37 deletions
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49
sys/vm/vm_swapout.c
View File

@ -173,51 +173,26 @@ static void vm_thread_swapout(struct thread *td);
static void
vm_swapout_object_deactivate_page(pmap_t pmap, vm_page_t m, bool unmap)
{
int act_delta;
if (vm_page_tryxbusy(m) == 0)
return;
VM_CNT_INC(v_pdpages);
/*
* The page may acquire a wiring after this check.
* The page daemon handles wired pages, so there is
* no harm done if a wiring appears while we are
* attempting to deactivate the page.
* Ignore unreclaimable wired pages. Repeat the check after busying
* since a busy holder may wire the page.
*/
if (vm_page_wired(m) || !vm_page_tryxbusy(m))
return;
if (vm_page_wired(m) || !pmap_page_exists_quick(pmap, m)) {
vm_page_xunbusy(m);
return;
}
act_delta = pmap_ts_referenced(m);
vm_page_lock(m);
if ((m->a.flags & PGA_REFERENCED) != 0) {
if (act_delta == 0)
act_delta = 1;
vm_page_aflag_clear(m, PGA_REFERENCED);
if (!pmap_is_referenced(m)) {
vm_page_lock(m);
if (!vm_page_active(m))
(void)vm_page_try_remove_all(m);
else if (unmap && vm_page_try_remove_all(m))
vm_page_deactivate(m);
vm_page_unlock(m);
}
if (!vm_page_active(m) && act_delta != 0) {
vm_page_activate(m);
m->a.act_count += act_delta;
} else if (vm_page_active(m)) {
/*
* The page daemon does not requeue pages
* after modifying their activation count.
*/
if (act_delta == 0) {
m->a.act_count -= min(m->a.act_count, ACT_DECLINE);
if (unmap && m->a.act_count == 0) {
(void)vm_page_try_remove_all(m);
vm_page_deactivate(m);
}
} else {
vm_page_activate(m);
if (m->a.act_count < ACT_MAX - ACT_ADVANCE)
m->a.act_count += ACT_ADVANCE;
}
} else if (vm_page_inactive(m))
(void)vm_page_try_remove_all(m);
vm_page_unlock(m);
vm_page_xunbusy(m);
}