[src/trunk]: src/sys/arch/x86/x86 Align the TLB packet precisely on the stack...

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details:   https://anonhg.NetBSD.org/src/rev/857b8b749e43
branches:  trunk
changeset: 1005678:857b8b749e43
user:      ad <ad%NetBSD.org@localhost>
date:      Mon Dec 16 19:17:25 2019 +0000

description:
Align the TLB packet precisely on the stack, and do 7 INVLPG since it's
what fits in a single line.

diffstat:

 sys/arch/x86/x86/x86_tlb.c |  41 +++++++++++++++++------------------------
 1 files changed, 17 insertions(+), 24 deletions(-)

diffs (113 lines):

diff -r b53dd6b6b837 -r 857b8b749e43 sys/arch/x86/x86/x86_tlb.c
--- a/sys/arch/x86/x86/x86_tlb.c        Mon Dec 16 18:50:44 2019 +0000
+++ b/sys/arch/x86/x86/x86_tlb.c        Mon Dec 16 19:17:25 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: x86_tlb.c,v 1.12 2019/12/02 20:59:56 pgoyette Exp $    */
+/*     $NetBSD: x86_tlb.c,v 1.13 2019/12/16 19:17:25 ad Exp $  */
 
 /*-
  * Copyright (c) 2008-2019 The NetBSD Foundation, Inc.
@@ -40,7 +40,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: x86_tlb.c,v 1.12 2019/12/02 20:59:56 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: x86_tlb.c,v 1.13 2019/12/16 19:17:25 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -66,10 +66,10 @@
  * until the request is completed.  This keeps the cache line in the shared
  * state, and bus traffic to a minimum.
  *
- * On i386 the packet is 28 bytes in size.  On amd64 it's 52 bytes.
+ * On i386 the packet is 32 bytes in size.  On amd64 it's 60 bytes.
  */
 typedef struct {
-       uintptr_t               tp_va[6];
+       uintptr_t               tp_va[7];
        uint8_t                 tp_count;
        uint8_t                 tp_userpmap;
        uint8_t                 tp_global;
@@ -77,23 +77,14 @@
 } pmap_tlb_packet_t;
 
 /*
- * Padded packet stored on the initiator's stack.
- */
-typedef struct {
-       uint8_t                 ts_pad1[COHERENCY_UNIT];
-       pmap_tlb_packet_t       ts_tp;
-       uint8_t                 ts_pad2[COHERENCY_UNIT];
-} pmap_tlb_stackbuf_t;
-
-/*
  * No more than N separate invlpg.
  *
- * Statistically, a value of six is big enough to cover the requested number
+ * Statistically, a value of 7 is big enough to cover the requested number
  * of pages in ~ 95% of the TLB shootdowns we are getting. We therefore rarely
  * reach the limit, and increasing it can actually reduce the performance due
  * to the high cost of invlpg.
  */
-#define        TP_MAXVA                6       /* for individual mappings */
+#define        TP_MAXVA                7       /* for individual mappings */
 #define        TP_ALLVA                255     /* special: shoot all mappings */
 
 /*
@@ -355,8 +346,8 @@
 void
 pmap_tlb_shootnow(void)
 {
-       volatile pmap_tlb_packet_t *tp;
-       volatile pmap_tlb_stackbuf_t ts;
+       volatile pmap_tlb_packet_t *tp, *ts;
+       volatile uint8_t stackbuf[128];
        struct cpu_info *ci;
        kcpuset_t *target;
        u_int local, rcpucount;
@@ -405,11 +396,13 @@
         * against an interrupt on the current CPU trying the same.
         */
        KASSERT(rcpucount < ncpu);
-       ts.ts_tp = *tp;
-       KASSERT(!ts.ts_tp.tp_done);
+       KASSERT(sizeof(*ts) <= (sizeof(stackbuf) / 2));
+       ts = (void *)roundup2((uintptr_t)stackbuf, (sizeof(stackbuf) / 2));
+       *ts = *tp;
+       KASSERT(!ts->tp_done);
        while (atomic_cas_ptr(&pmap_tlb_packet, NULL,
-           __UNVOLATILE(&ts.ts_tp)) != NULL) {
-               KASSERT(pmap_tlb_packet != &ts.ts_tp);
+           __UNVOLATILE(ts)) != NULL) {
+               KASSERT(pmap_tlb_packet != ts);
                /*
                 * Don't bother with exponentional backoff, as the pointer
                 * is in a dedicated cache line and only updated twice per
@@ -439,7 +432,7 @@
         */
        pmap_tlb_pendcount = rcpucount;
        pmap_tlb_evcnt.ev_count++;
-       pmap_tlb_processpacket(&ts.ts_tp, target);
+       pmap_tlb_processpacket(ts, target);
 
        /*
         * Clear out the local CPU's buffer for the next user.  Once done,
@@ -461,7 +454,7 @@
         * perform local shootdown if needed, using our copy of the packet.
         */
        if (local) {
-               pmap_tlb_invalidate(&ts.ts_tp);
+               pmap_tlb_invalidate(ts);
        }
 
        /*
@@ -470,7 +463,7 @@
         * CPU out will update it and only we are reading it).  No memory
         * barrier required due to prior stores - yay x86.
         */
-       while (!ts.ts_tp.tp_done) {
+       while (!ts->tp_done) {
                x86_pause();
        }
 }