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[src/trunk]: src/usr.bin/vmstat Remove PG_ZERO. It worked brilliantly on x86...



details:   https://anonhg.NetBSD.org/src/rev/ea7d1f33691c
branches:  trunk
changeset: 972968:ea7d1f33691c
user:      ad <ad%NetBSD.org@localhost>
date:      Sun Jun 14 21:41:42 2020 +0000

description:
Remove PG_ZERO.  It worked brilliantly on x86 machines from the mid-90s but
having spent an age experimenting with it over the last 6 months on various
machines and with different use cases it's always either break-even or a
slight net loss for me.

diffstat:

 sys/arch/x86/x86/pmap.c |   7 +---
 sys/sys/cpu_data.h      |   8 ++--
 sys/uvm/uvm_glue.c      |   7 +---
 sys/uvm/uvm_meter.c     |  16 +---------
 sys/uvm/uvm_page.c      |  72 ++++++++----------------------------------------
 sys/uvm/uvm_page.h      |  15 +---------
 sys/uvm/uvm_pgflcache.c |  10 +++---
 sys/uvm/uvm_pglist.c    |   6 +--
 sys/uvm/uvm_stat.c      |   9 ++---
 usr.bin/vmstat/vmstat.c |  15 +--------
 10 files changed, 37 insertions(+), 128 deletions(-)

diffs (truncated from 533 to 300 lines):

diff -r f6a49bb85868 -r ea7d1f33691c sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Sun Jun 14 21:34:25 2020 +0000
+++ b/sys/arch/x86/x86/pmap.c   Sun Jun 14 21:41:42 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.398 2020/06/03 00:27:46 ad Exp $    */
+/*     $NetBSD: pmap.c,v 1.399 2020/06/14 21:41:42 ad Exp $    */
 
 /*
  * Copyright (c) 2008, 2010, 2016, 2017, 2019, 2020 The NetBSD Foundation, Inc.
@@ -130,7 +130,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.398 2020/06/03 00:27:46 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.399 2020/06/14 21:41:42 ad Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -3066,7 +3066,6 @@
                if (!pmap_valid_entry(opte)) {
                        continue;
                }
-               pmap_pte_set(pte, 0);
 
                /*
                 * Count the PTE.  If it's not for a managed mapping
@@ -5741,8 +5740,6 @@
                PMAP_DUMMY_LOCK(pmap);
                uvm_pagerealloc(ptp, NULL, 0);
                PMAP_DUMMY_UNLOCK(pmap);
-
-               ptp->flags |= PG_ZERO;
                uvm_pagefree(ptp);
        }
        mutex_exit(&pmap->pm_lock);
diff -r f6a49bb85868 -r ea7d1f33691c sys/sys/cpu_data.h
--- a/sys/sys/cpu_data.h        Sun Jun 14 21:34:25 2020 +0000
+++ b/sys/sys/cpu_data.h        Sun Jun 14 21:41:42 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: cpu_data.h,v 1.51 2020/06/11 22:21:05 ad Exp $ */
+/*     $NetBSD: cpu_data.h,v 1.52 2020/06/14 21:41:42 ad Exp $ */
 
 /*-
  * Copyright (c) 2004, 2006, 2007, 2008, 2019, 2020 The NetBSD Foundation, Inc.
@@ -57,12 +57,12 @@
        CPU_COUNT_FORKS_SHAREVM,
        CPU_COUNT_COLORHIT,             /* 8 */
        CPU_COUNT_COLORMISS,
-       CPU_COUNT_PGA_ZEROHIT,
-       CPU_COUNT_PGA_ZEROMISS,
+       CPU_COUNT__UNUSED3,
+       CPU_COUNT__UNUSED4,
        CPU_COUNT_CPUHIT,
        CPU_COUNT_CPUMISS,
        CPU_COUNT_FREEPAGES,
-       CPU_COUNT_ZEROPAGES,
+       CPU_COUNT__UNUSED5,
        CPU_COUNT_PAGEINS,              /* 16 */
        CPU_COUNT_FLTUP,
        CPU_COUNT_FLTNOUP,
diff -r f6a49bb85868 -r ea7d1f33691c sys/uvm/uvm_glue.c
--- a/sys/uvm/uvm_glue.c        Sun Jun 14 21:34:25 2020 +0000
+++ b/sys/uvm/uvm_glue.c        Sun Jun 14 21:41:42 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_glue.c,v 1.180 2020/06/11 19:20:47 ad Exp $        */
+/*     $NetBSD: uvm_glue.c,v 1.181 2020/06/14 21:41:42 ad Exp $        */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_glue.c,v 1.180 2020/06/11 19:20:47 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_glue.c,v 1.181 2020/06/14 21:41:42 ad Exp $");
 
 #include "opt_kgdb.h"
 #include "opt_kstack.h"
@@ -531,7 +531,4 @@
 
        if (!ci->ci_want_resched)
                uvmpdpol_idle(ucpu);
-       if (!ci->ci_want_resched)
-               uvm_pageidlezero();
-
 }
diff -r f6a49bb85868 -r ea7d1f33691c sys/uvm/uvm_meter.c
--- a/sys/uvm/uvm_meter.c       Sun Jun 14 21:34:25 2020 +0000
+++ b/sys/uvm/uvm_meter.c       Sun Jun 14 21:41:42 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_meter.c,v 1.79 2020/06/11 22:21:05 ad Exp $        */
+/*     $NetBSD: uvm_meter.c,v 1.80 2020/06/14 21:41:42 ad Exp $        */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -36,7 +36,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_meter.c,v 1.79 2020/06/11 22:21:05 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_meter.c,v 1.80 2020/06/14 21:41:42 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -111,7 +111,6 @@
        u.inactive = inactive;
        u.paging = uvmexp.paging;
        u.wired = uvmexp.wired;
-       u.zeropages = cpu_count_get(CPU_COUNT_ZEROPAGES);
        u.reserve_pagedaemon = uvmexp.reserve_pagedaemon;
        u.reserve_kernel = uvmexp.reserve_kernel;
        u.freemin = uvmexp.freemin;
@@ -137,8 +136,6 @@
        u.forks = cpu_count_get(CPU_COUNT_FORKS);
        u.forks_ppwait = cpu_count_get(CPU_COUNT_FORKS_PPWAIT);
        u.forks_sharevm = cpu_count_get(CPU_COUNT_FORKS_SHAREVM);
-       u.pga_zerohit = cpu_count_get(CPU_COUNT_PGA_ZEROHIT);
-       u.pga_zeromiss = cpu_count_get(CPU_COUNT_PGA_ZEROMISS);
        u.zeroaborts = uvmexp.zeroaborts;
        u.fltnoram = cpu_count_get(CPU_COUNT_FLTNORAM);
        u.fltnoanon = cpu_count_get(CPU_COUNT_FLTNOANON);
@@ -273,12 +270,6 @@
                       NULL, USPACE, NULL, 0,
                       CTL_VM, VM_USPACE, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
-                      CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
-                      CTLTYPE_BOOL, "idlezero",
-                      SYSCTL_DESCR("Whether try to zero pages in idle loop"),
-                      NULL, 0, &vm_page_zero_enable, 0,
-                      CTL_VM, CTL_CREATE, CTL_EOL);
-       sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE,
                       CTLTYPE_LONG, "minaddress",
                       SYSCTL_DESCR("Minimum user address"),
@@ -455,7 +446,6 @@
 
        /* uvm_availmem() will sync the counters if old. */
        uvmexp.free = (int)uvm_availmem(true);
-       uvmexp.zeropages = (int)cpu_count_get(CPU_COUNT_ZEROPAGES);
        uvmexp.cpuhit = (int)cpu_count_get(CPU_COUNT_CPUHIT);
        uvmexp.cpumiss = (int)cpu_count_get(CPU_COUNT_CPUMISS);
        uvmexp.faults = (int)cpu_count_get(CPU_COUNT_NFAULT);
@@ -468,8 +458,6 @@
        uvmexp.forks = (int)cpu_count_get(CPU_COUNT_FORKS);
        uvmexp.forks_ppwait = (int)cpu_count_get(CPU_COUNT_FORKS_PPWAIT);
        uvmexp.forks_sharevm = (int)cpu_count_get(CPU_COUNT_FORKS_SHAREVM);
-       uvmexp.pga_zerohit = (int)cpu_count_get(CPU_COUNT_PGA_ZEROHIT);
-       uvmexp.pga_zeromiss = (int)cpu_count_get(CPU_COUNT_PGA_ZEROMISS);
        uvmexp.fltnoram = (int)cpu_count_get(CPU_COUNT_FLTNORAM);
        uvmexp.fltnoanon = (int)cpu_count_get(CPU_COUNT_FLTNOANON);
        uvmexp.fltpgwait = (int)cpu_count_get(CPU_COUNT_FLTPGWAIT);
diff -r f6a49bb85868 -r ea7d1f33691c sys/uvm/uvm_page.c
--- a/sys/uvm/uvm_page.c        Sun Jun 14 21:34:25 2020 +0000
+++ b/sys/uvm/uvm_page.c        Sun Jun 14 21:41:42 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_page.c,v 1.241 2020/06/13 19:55:39 ad Exp $        */
+/*     $NetBSD: uvm_page.c,v 1.242 2020/06/14 21:41:42 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 1.241 2020/06/13 19:55:39 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.242 2020/06/14 21:41:42 ad Exp $");
 
 #include "opt_ddb.h"
 #include "opt_uvm.h"
@@ -119,13 +119,6 @@
 #include <uvm/uvm_pgflcache.h>
 
 /*
- * Some supported CPUs in a given architecture don't support all
- * of the things necessary to do idle page zero'ing efficiently.
- * We therefore provide a way to enable it from machdep code here.
- */
-bool vm_page_zero_enable = false;
-
-/*
  * number of pages per-CPU to reserve for the kernel.
  */
 #ifndef        UVM_RESERVED_PAGES_PER_CPU
@@ -1078,8 +1071,8 @@
                         * lock because of uvm_pglistalloc().
                         */
                        LIST_REMOVE(pg, pageq.list);
-                       KASSERT(pg->flags & PG_FREE);
-                       pg->flags &= PG_ZERO;
+                       KASSERT(pg->flags == PG_FREE);
+                       pg->flags = PG_BUSY | PG_CLEAN | PG_FAKE;
                        pgb->pgb_nfree--;
 
                        /*
@@ -1154,8 +1147,8 @@
  * => caller must activate/deactivate page if it is not wired.
  * => free_list is ignored if strat == UVM_PGA_STRAT_NORMAL.
  * => policy decision: it is more important to pull a page off of the
- *     appropriate priority free list than it is to get a zero'd or
- *     unknown contents page.  This is because we live with the
+ *     appropriate priority free list than it is to get a page from the
+ *     correct bucket or color bin.  This is because we live with the
  *     consequences of a bad free list decision for the entire
  *     lifetime of the page, e.g. if the page comes from memory that
  *     is slower to access.
@@ -1165,8 +1158,7 @@
 uvm_pagealloc_strat(struct uvm_object *obj, voff_t off, struct vm_anon *anon,
     int flags, int strat, int free_list)
 {
-       int zeroit = 0, color;
-       int lcv, error, s;
+       int color, lcv, error, s;
        struct uvm_cpu *ucpu;
        struct vm_page *pg;
        lwp_t *l;
@@ -1280,28 +1272,15 @@
        ucpu->pgflcolor = (color + 1) & uvmexp.colormask;
 
        /*
-        * while still at IPL_VM, update allocation statistics and remember
-        * if we have to zero the page
+        * while still at IPL_VM, update allocation statistics.
         */
 
        CPU_COUNT(CPU_COUNT_FREEPAGES, -1);
-       if (flags & UVM_PGA_ZERO) {
-               if (pg->flags & PG_ZERO) {
-                       CPU_COUNT(CPU_COUNT_PGA_ZEROHIT, 1);
-                       zeroit = 0;
-               } else {
-                       CPU_COUNT(CPU_COUNT_PGA_ZEROMISS, 1);
-                       zeroit = 1;
-               }
-       }
-       if (pg->flags & PG_ZERO) {
-               CPU_COUNT(CPU_COUNT_ZEROPAGES, -1);
-       }
        if (anon) {
                CPU_COUNT(CPU_COUNT_ANONCLEAN, 1);
        }
        splx(s);
-       KASSERT((pg->flags & ~(PG_ZERO|PG_FREE)) == 0);
+       KASSERT(pg->flags == (PG_BUSY|PG_CLEAN|PG_FAKE));
 
        /*
         * assign the page to the object.  as the page was free, we know
@@ -1315,7 +1294,6 @@
        pg->uobject = obj;
        pg->uanon = anon;
        KASSERT(uvm_page_owner_locked_p(pg, true));
-       pg->flags = PG_BUSY|PG_CLEAN|PG_FAKE;
        if (anon) {
                anon->an_page = pg;
                pg->flags |= PG_ANON;
@@ -1347,16 +1325,11 @@
        UVM_PAGE_OWN(pg, "new alloc");
 
        if (flags & UVM_PGA_ZERO) {
-               /*
-                * A zero'd page is not clean.  If we got a page not already
-                * zero'd, then we have to zero it ourselves.
-                */
+               /* A zero'd page is not clean. */
                if (obj != NULL || anon != NULL) {
                        uvm_pagemarkdirty(pg, UVM_PAGE_STATUS_DIRTY);
                }
-               if (zeroit) {
-                       pmap_zero_page(VM_PAGE_TO_PHYS(pg));
-               }
+               pmap_zero_page(VM_PAGE_TO_PHYS(pg));
        }
 
        return(pg);
@@ -1477,7 +1450,7 @@
        pmap_update(pmap_kernel());
        while (p < ep) {
                if (*p != 0)
-                       panic("PG_ZERO page isn't zero-filled");
+                       panic("zero page isn't zero-filled");
                p++;
        }
        pmap_kremove(uvm_zerocheckkva, PAGE_SIZE);
@@ -1633,16 +1606,11 @@
 #ifdef DEBUG
        pg->uobject = (void *)0xdeadbeef;
        pg->uanon = (void *)0xdeadbeef;
-       if (pg->flags & PG_ZERO)
-               uvm_pagezerocheck(pg);
 #endif /* DEBUG */
 
        /* Try to send the page to the per-CPU cache. */
        s = splvm();
        CPU_COUNT(CPU_COUNT_FREEPAGES, 1);
-       if (pg->flags & PG_ZERO) {
-               CPU_COUNT(CPU_COUNT_ZEROPAGES, 1);
-       }
        ucpu = curcpu()->ci_data.cpu_uvm;
        bucket = uvm_page_get_bucket(pg);
        if (bucket == ucpu->pgflbucket && uvm_pgflcache_free(ucpu, pg)) {
@@ -1657,7 +1625,7 @@



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