[src/trunk]: src/sys/arch/x86/x86 Use pmap_bootstrap_valloc and simplify. By ...

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

details:   https://anonhg.NetBSD.org/src/rev/6cbafec69fa7
branches:  trunk
changeset: 819788:6cbafec69fa7
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Dec 17 13:43:33 2016 +0000

description:
Use pmap_bootstrap_valloc and simplify. By the way, I think the cache
stuff is wrong, since the pte is not necessarily aligned to 64 bytes, so
nothing guarantees there is no false sharing.

diffstat:

 sys/arch/x86/x86/pmap.c |  61 +++++++++++++++++++-----------------------------
 1 files changed, 24 insertions(+), 37 deletions(-)

diffs (96 lines):

diff -r 5cf0255b5b86 -r 6cbafec69fa7 sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Sat Dec 17 12:11:38 2016 +0000
+++ b/sys/arch/x86/x86/pmap.c   Sat Dec 17 13:43:33 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.232 2016/12/16 19:52:22 maxv Exp $  */
+/*     $NetBSD: pmap.c,v 1.233 2016/12/17 13:43:33 maxv Exp $  */
 
 /*-
  * Copyright (c) 2008, 2010, 2016 The NetBSD Foundation, Inc.
@@ -171,7 +171,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.232 2016/12/16 19:52:22 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.233 2016/12/17 13:43:33 maxv Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -1351,46 +1351,33 @@
 
        /*
         * Now we allocate the "special" VAs which are used for tmp mappings
-        * by the pmap (and other modules). We allocate the VAs by advancing
-        * virtual_avail (note that there are no pages mapped at these VAs).
-        * we find the PTE that maps the allocated VA via the linear PTE
-        * mapping.
+        * by pmap. We allocate the VAs, and find the PTE that maps them via
+        * the linear PTE mapping.
         */
-
-       pt_entry_t *pte = PTE_BASE + pl1_i(virtual_avail);
+       vaddr_t cpuva_base;
+       pt_entry_t *pte;
 
 #ifdef MULTIPROCESSOR
        /*
-        * Waste some VA space to avoid false sharing of cache lines
-        * for page table pages: Give each possible CPU a cache line
-        * of PTE's (8) to play with, though we only need 4.  We could
-        * recycle some of this waste by putting the idle stacks here
-        * as well; we could waste less space if we knew the largest
-        * CPU ID beforehand.
+        * Waste some VA space to avoid false sharing of cache lines for page
+        * table pages: give each possible CPU a cache line of 8 PTEs to play
+        * with, though we only need 4.
         */
-       csrcp = (char *) virtual_avail;  csrc_pte = pte;
-
-       cdstp = (char *) virtual_avail+PAGE_SIZE;  cdst_pte = pte+1;
-
-       zerop = (char *) virtual_avail+PAGE_SIZE*2;  zero_pte = pte+2;
-
-       ptpp = (char *) virtual_avail+PAGE_SIZE*3;  ptp_pte = pte+3;
-
-       virtual_avail += PAGE_SIZE * maxcpus * NPTECL;
-       pte += maxcpus * NPTECL;
+       cpuva_base = pmap_bootstrap_valloc(maxcpus * NPTECL);
 #else
-       csrcp = (void *) virtual_avail;  csrc_pte = pte;        /* allocate */
-       virtual_avail += PAGE_SIZE; pte++;                      /* advance */
-
-       cdstp = (void *) virtual_avail;  cdst_pte = pte;
-       virtual_avail += PAGE_SIZE; pte++;
-
-       zerop = (void *) virtual_avail;  zero_pte = pte;
-       virtual_avail += PAGE_SIZE; pte++;
-
-       ptpp = (void *) virtual_avail;  ptp_pte = pte;
-       virtual_avail += PAGE_SIZE; pte++;
+       cpuva_base = pmap_bootstrap_valloc(4);
 #endif
+       pte = PTE_BASE + pl1_i(cpuva_base);
+
+       /* Values used to index the array */
+       csrcp = (char *)cpuva_base;
+       csrc_pte = pte;
+       cdstp = (char *)cpuva_base + PAGE_SIZE;
+       cdst_pte = pte + 1;
+       zerop = (char *)cpuva_base + PAGE_SIZE * 2;
+       zero_pte = pte + 2;
+       ptpp = (char *)cpuva_base + PAGE_SIZE * 3;
+       ptp_pte = pte + 3;
 
        if (VM_MIN_KERNEL_ADDRESS == KERNBASE) {
                early_zerop = zerop;
@@ -3152,8 +3139,8 @@
 
        kpreempt_disable();
        id = cpu_number();
-       spte = PTESLEW(csrc_pte,id);
-       dpte = PTESLEW(cdst_pte,id);
+       spte = PTESLEW(csrc_pte, id);
+       dpte = PTESLEW(cdst_pte, id);
        csrcva = VASLEW(csrcp, id);
        cdstva = VASLEW(cdstp, id);