Author: alc
Date: Sun Sep 4 22:08:04 2016
New Revision: 305398
URL: https://svnweb.freebsd.org/changeset/base/305398
Log:
Replace the number 4 in pmap_ts_referenced() by PMAP_TS_REFERENCED_MAX,
like we've done elsewhere, e.g., amd64.
As an optimization to the machine-independent layer, change the machine-
dependent pmap_ts_referenced() so that it updates the page's dirty field
if a modified bit is found while counting reference bits. This
opportunistic update can be performed at low cost and can eliminate the
need for some future calls to pmap_is_modified() by the machine-
independent layer.
MFC after: 3 weeks
Modified:
head/sys/sparc64/sparc64/pmap.c
Modified: head/sys/sparc64/sparc64/pmap.c
==============================================================================
--- head/sys/sparc64/sparc64/pmap.c Sun Sep 4 21:54:24 2016
(r305397)
+++ head/sys/sparc64/sparc64/pmap.c Sun Sep 4 22:08:04 2016
(r305398)
@@ -2073,6 +2073,8 @@ pmap_page_is_mapped(vm_page_t m)
return (rv);
}
+#define PMAP_TS_REFERENCED_MAX 5
+
/*
* Return a count of reference bits for a page, clearing those bits.
* It is not necessary for every reference bit to be cleared, but it
@@ -2082,6 +2084,14 @@ pmap_page_is_mapped(vm_page_t m)
* XXX: The exact number of bits to check and clear is a matter that
* should be tested and standardized at some point in the future for
* optimal aging of shared pages.
+ *
+ * As an optimization, update the page's dirty field if a modified bit is
+ * found while counting reference bits. This opportunistic update can be
+ * performed at low cost and can eliminate the need for some future calls
+ * to pmap_is_modified(). However, since this function stops after
+ * finding PMAP_TS_REFERENCED_MAX reference bits, it may not detect some
+ * dirty pages. Those dirty pages will only be detected by a future call
+ * to pmap_is_modified().
*/
int
pmap_ts_referenced(vm_page_t m)
@@ -2105,7 +2115,10 @@ pmap_ts_referenced(vm_page_t m)
if ((tp->tte_data & TD_PV) == 0)
continue;
data = atomic_clear_long(&tp->tte_data, TD_REF);
- if ((data & TD_REF) != 0 && ++count > 4)
+ if ((data & TD_W) != 0)
+ vm_page_dirty(m);
+ if ((data & TD_REF) != 0 && ++count >=
+ PMAP_TS_REFERENCED_MAX)
break;
} while ((tp = tpn) != NULL && tp != tpf);
}
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