[src/trunk]: src/sys/kern Use __read_mostly and gather related __cacheline_al...

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

details:   https://anonhg.NetBSD.org/src/rev/3007c2870432
branches:  trunk
changeset: 744427:3007c2870432
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sat Feb 01 12:51:18 2020 +0000

description:
Use __read_mostly and gather related __cacheline_aligned together.

Should save a few bytes of kernel.

diffstat:

 sys/kern/subr_percpu.c |  28 +++++++++++++++-------------
 1 files changed, 15 insertions(+), 13 deletions(-)

diffs (77 lines):

diff -r cb9ffc63e280 -r 3007c2870432 sys/kern/subr_percpu.c
--- a/sys/kern/subr_percpu.c    Sat Feb 01 12:49:02 2020 +0000
+++ b/sys/kern/subr_percpu.c    Sat Feb 01 12:51:18 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_percpu.c,v 1.21 2020/02/01 12:49:02 riastradh Exp $       */
+/*     $NetBSD: subr_percpu.c,v 1.22 2020/02/01 12:51:18 riastradh Exp $       */
 
 /*-
  * Copyright (c)2007,2008 YAMAMOTO Takashi,
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_percpu.c,v 1.21 2020/02/01 12:49:02 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_percpu.c,v 1.22 2020/02/01 12:51:18 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/cpu.h>
@@ -55,9 +55,11 @@
 };
 
 static krwlock_t       percpu_swap_lock        __cacheline_aligned;
-static kmutex_t                percpu_allocation_lock  __cacheline_aligned;
-static vmem_t *                percpu_offset_arena     __cacheline_aligned;
-static unsigned int    percpu_nextoff          __cacheline_aligned;
+static vmem_t *                percpu_offset_arena     __read_mostly;
+static struct {
+       kmutex_t        lock;
+       unsigned int    nextoff;
+} percpu_allocation __cacheline_aligned;
 
 static percpu_cpu_t *
 cpu_percpu(struct cpu_info *ci)
@@ -71,7 +73,7 @@
 {
        const unsigned int off = pc->pc_offset;
 
-       KASSERT(off < percpu_nextoff);
+       KASSERT(off < percpu_allocation.nextoff);
        return off;
 }
 
@@ -172,10 +174,10 @@
                return ENOMEM;
 
        size = roundup(size, PERCPU_IMPORT_SIZE);
-       mutex_enter(&percpu_allocation_lock);
-       offset = percpu_nextoff;
-       percpu_nextoff = nextoff = percpu_nextoff + size;
-       mutex_exit(&percpu_allocation_lock);
+       mutex_enter(&percpu_allocation.lock);
+       offset = percpu_allocation.nextoff;
+       percpu_allocation.nextoff = nextoff = percpu_allocation.nextoff + size;
+       mutex_exit(&percpu_allocation.lock);
 
        percpu_cpu_enlarge(nextoff);
 
@@ -213,8 +215,8 @@
 
        ASSERT_SLEEPABLE();
        rw_init(&percpu_swap_lock);
-       mutex_init(&percpu_allocation_lock, MUTEX_DEFAULT, IPL_NONE);
-       percpu_nextoff = PERCPU_QUANTUM_SIZE;
+       mutex_init(&percpu_allocation.lock, MUTEX_DEFAULT, IPL_NONE);
+       percpu_allocation.nextoff = PERCPU_QUANTUM_SIZE;
 
        percpu_offset_arena = vmem_xcreate("percpu", 0, 0, PERCPU_QUANTUM_SIZE,
            percpu_backend_alloc, NULL, NULL, PERCPU_QCACHE_MAX, VM_SLEEP,
@@ -231,7 +233,7 @@
 percpu_init_cpu(struct cpu_info *ci)
 {
        percpu_cpu_t * const pcc = cpu_percpu(ci);
-       size_t size = percpu_nextoff; /* XXX racy */
+       size_t size = percpu_allocation.nextoff; /* XXX racy */
 
        ASSERT_SLEEPABLE();
        pcc->pcc_size = size;