[src/trunk]: src/sys/uvm uvmpdpol_pageactive(): the change to not re-activate...

[ad <ad%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/02ff3cd4bfe6
branches:  trunk
changeset: 848237:02ff3cd4bfe6
user:      ad <ad%NetBSD.org@localhost>
date:      Tue Jan 21 20:37:06 2020 +0000

description:
uvmpdpol_pageactive(): the change to not re-activate recently activated
pages worked great with uvm_pageqlock, but it doesn't buy anything any more,
because now the busy pages are likely in a per-CPU queue somewhere waiting
to be processed, and changing the intent on those queued pages costs next
to nothing.  Remove this and get back all the bits in pg->pqflags.

diffstat:

 sys/uvm/uvm_page.c           |  20 ++++++++++++--------
 sys/uvm/uvm_page.h           |  18 ++++++++++--------
 sys/uvm/uvm_pdpolicy_clock.c |  21 ++++-----------------
 3 files changed, 26 insertions(+), 33 deletions(-)

diffs (153 lines):

diff -r 423308320110 -r 02ff3cd4bfe6 sys/uvm/uvm_page.c
--- a/sys/uvm/uvm_page.c        Tue Jan 21 20:31:57 2020 +0000
+++ b/sys/uvm/uvm_page.c        Tue Jan 21 20:37:06 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_page.c,v 1.224 2020/01/15 17:55:45 ad Exp $        */
+/*     $NetBSD: uvm_page.c,v 1.225 2020/01/21 20:37:06 ad Exp $        */
 
 /*-
  * Copyright (c) 2019, 2020 The NetBSD Foundation, Inc.
@@ -95,7 +95,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.224 2020/01/15 17:55:45 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.225 2020/01/21 20:37:06 ad Exp $");
 
 #include "opt_ddb.h"
 #include "opt_uvm.h"
@@ -2149,6 +2149,7 @@
  */
 
 static const char page_flagbits[] = UVM_PGFLAGBITS;
+static const char page_pqflagbits[] = UVM_PQFLAGBITS;
 
 void
 uvm_page_printit(struct vm_page *pg, bool full,
@@ -2162,12 +2163,15 @@
 
        (*pr)("PAGE %p:\n", pg);
        snprintb(pgbuf, sizeof(pgbuf), page_flagbits, pg->flags);
-       (*pr)("  flags=%s\n  pqflags=%x, wire_count=%d, pa=0x%lx\n",
-           pgbuf, pg->pqflags, pg->wire_count, (long)VM_PAGE_TO_PHYS(pg));
-       (*pr)("  uobject=%p, uanon=%p, offset=0x%llx loan_count=%d\n",
-           pg->uobject, pg->uanon, (long long)pg->offset, pg->loan_count);
-       (*pr)("  bucket=%d freelist=%d\n",
-           uvm_page_get_bucket(pg), uvm_page_get_freelist(pg));
+       (*pr)("  flags=%s\n", pgbuf);
+       snprintb(pgbuf, sizeof(pgbuf), page_pqflagbits, pg->pqflags);
+       (*pr)("  pqflags=%s\n", pgbuf);
+       (*pr)("  uobject=%p, uanon=%p, offset=0x%llx\n",
+           pg->uobject, pg->uanon, (long long)pg->offset);
+       (*pr)("  loan_count=%d wire_count=%d bucket=%d freelist=%d\n",
+           pg->loan_count, pg->wire_count, uvm_page_get_bucket(pg),
+           uvm_page_get_freelist(pg));
+       (*pr)("  pa=0x%lx\n", (long)VM_PAGE_TO_PHYS(pg));
 #if defined(UVM_PAGE_TRKOWN)
        if (pg->flags & PG_BUSY)
                (*pr)("  owning process = %d, tag=%s\n",
diff -r 423308320110 -r 02ff3cd4bfe6 sys/uvm/uvm_page.h
--- a/sys/uvm/uvm_page.h        Tue Jan 21 20:31:57 2020 +0000
+++ b/sys/uvm/uvm_page.h        Tue Jan 21 20:37:06 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_page.h,v 1.96 2020/01/15 17:55:45 ad Exp $ */
+/*     $NetBSD: uvm_page.h,v 1.97 2020/01/21 20:37:06 ad Exp $ */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -181,7 +181,7 @@
 };
 
 /*
- * Overview of UVM page flags.
+ * Overview of UVM page flags, stored in pg->flags.
  *
  * Locking notes:
  *
@@ -275,12 +275,9 @@
        "\21PAGER1"
 
 /*
- * uvmpdpol state flags.
+ * Flags stored in pg->pqflags, which is protected by pg->interlock.
  *
- * => may only be changed with pg->interlock held.
- * => changing them is the responsibility of uvmpdpol ..
- * => .. but uvm_page needs to know about them in order to purge updates.
- * => PQ_PRIVATE is private to the individual uvmpdpol implementation.
+ * PQ_PRIVATE is for uvmpdpol to do whatever it wants with.
  */
 
 #define        PQ_INTENT_A             0x00000000      /* intend activation */
@@ -290,7 +287,12 @@
 #define        PQ_INTENT_MASK          0x00000003      /* mask of intended state */
 #define        PQ_INTENT_SET           0x00000004      /* not realized yet */
 #define        PQ_INTENT_QUEUED        0x00000008      /* queued for processing */
-#define        PQ_PRIVATE              0xfffffff0
+#define        PQ_PRIVATE              0x00000ff0      /* private for pdpolicy */
+
+#define        UVM_PQFLAGBITS \
+       "\20\1INTENT_0\2INTENT_1\3INTENT_SET\4INTENT_QUEUED" \
+       "\5PRIVATE1\6PRIVATE2\7PRIVATE3\10PRIVATE4" \
+       "\11PRIVATE5\12PRIVATE6\13PRIVATE7\14PRIVATE8"
 
 /*
  * physical memory layout structure
diff -r 423308320110 -r 02ff3cd4bfe6 sys/uvm/uvm_pdpolicy_clock.c
--- a/sys/uvm/uvm_pdpolicy_clock.c      Tue Jan 21 20:31:57 2020 +0000
+++ b/sys/uvm/uvm_pdpolicy_clock.c      Tue Jan 21 20:37:06 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_pdpolicy_clock.c,v 1.30 2020/01/01 14:33:48 ad Exp $       */
+/*     $NetBSD: uvm_pdpolicy_clock.c,v 1.31 2020/01/21 20:37:06 ad Exp $       */
 /*     NetBSD: uvm_pdaemon.c,v 1.72 2006/01/05 10:47:33 yamt Exp $     */
 
 /*-
@@ -98,7 +98,7 @@
 #else /* defined(PDSIM) */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_pdpolicy_clock.c,v 1.30 2020/01/01 14:33:48 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_pdpolicy_clock.c,v 1.31 2020/01/21 20:37:06 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -124,7 +124,6 @@
 #define        CLOCK_PDQ_SIZE  128
 #endif /* !defined(CLOCK_PDQ_SIZE) */
 
-#define        PQ_TIME         0xffffffc0      /* time of last activation */
 #define PQ_INACTIVE    0x00000010      /* page is in inactive list */
 #define PQ_ACTIVE      0x00000020      /* page is in active list */
 
@@ -487,29 +486,17 @@
        uvmpdpol_pagedequeue_locked(pg);
        TAILQ_INSERT_TAIL(&pdpol_state.s_activeq, pg, pdqueue);
        pdpol_state.s_active++;
-       pg->pqflags = (pg->pqflags & PQ_INTENT_QUEUED) | PQ_ACTIVE |
-           (hardclock_ticks & PQ_TIME);
+       pg->pqflags = (pg->pqflags & PQ_INTENT_QUEUED) | PQ_ACTIVE;
 }
 
 void
 uvmpdpol_pageactivate(struct vm_page *pg)
 {
-       uint32_t pqflags;
 
        KASSERT(uvm_page_owner_locked_p(pg));
        KASSERT(mutex_owned(&pg->interlock));
 
-       /*
-        * if there is any intent set on the page, or the page is not
-        * active, or the page was activated in the "distant" past, then
-        * it needs to be activated anew.
-        */
-       pqflags = pg->pqflags;
-       if ((pqflags & PQ_INTENT_SET) != 0 ||
-           (pqflags & PQ_ACTIVE) == 0 ||
-           ((hardclock_ticks & PQ_TIME) - (pqflags & PQ_TIME)) > hz) {
-               uvmpdpol_set_intent(pg, PQ_INTENT_A);
-       }
+       uvmpdpol_set_intent(pg, PQ_INTENT_A);
 }
 
 static void