Author: markj
Date: Sat Dec 28 19:03:17 2019
New Revision: 356154
URL: https://svnweb.freebsd.org/changeset/base/356154
Log:
Don't update per-page activation counts in the swapout code.
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
Modified:
head/sys/vm/vm_swapout.c
Modified: head/sys/vm/vm_swapout.c
==============================================================================
--- head/sys/vm/vm_swapout.c Sat Dec 28 18:08:26 2019 (r356153)
+++ head/sys/vm/vm_swapout.c Sat Dec 28 19:03:17 2019 (r356154)
@@ -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);
}
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