Author: mdf
Date: Fri May 13 18:48:00 2011
New Revision: 221853
URL: http://svn.freebsd.org/changeset/base/221853
Log:
Usa a globally visible region of zeros for both /dev/zero and the md
device. There are likely other kernel uses of "blob of zeros" than can
be converted.
Reviewed by: alc
MFC after: 1 week
Modified:
head/sys/dev/md/md.c
head/sys/dev/null/null.c
head/sys/sys/systm.h
head/sys/vm/vm_kern.c
Modified: head/sys/dev/md/md.c
==============================================================================
--- head/sys/dev/md/md.c Fri May 13 18:46:20 2011 (r221852)
+++ head/sys/dev/md/md.c Fri May 13 18:48:00 2011 (r221853)
@@ -205,9 +205,6 @@ struct md_s {
vm_object_t object;
};
-/* Used for BIO_DELETE on MD_VNODE */
-static u_char zero[PAGE_SIZE];
-
static struct indir *
new_indir(u_int shift)
{
@@ -560,7 +557,8 @@ mdstart_vnode(struct md_s *sc, struct bi
* that the two cases end up having very little in common.
*/
if (bp->bio_cmd == BIO_DELETE) {
- zerosize = sizeof(zero) - (sizeof(zero) % sc->sectorsize);
+ zerosize = ZERO_REGION_SIZE -
+ (ZERO_REGION_SIZE % sc->sectorsize);
auio.uio_iov = &aiov;
auio.uio_iovcnt = 1;
auio.uio_offset = (vm_ooffset_t)bp->bio_offset;
@@ -573,7 +571,7 @@ mdstart_vnode(struct md_s *sc, struct bi
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
error = 0;
while (auio.uio_offset < end) {
- aiov.iov_base = zero;
+ aiov.iov_base = __DECONST(void *, zero_region);
aiov.iov_len = end - auio.uio_offset;
if (aiov.iov_len > zerosize)
aiov.iov_len = zerosize;
Modified: head/sys/dev/null/null.c
==============================================================================
--- head/sys/dev/null/null.c Fri May 13 18:46:20 2011 (r221852)
+++ head/sys/dev/null/null.c Fri May 13 18:48:00 2011 (r221853)
@@ -65,8 +65,6 @@ static struct cdevsw zero_cdevsw = {
.d_flags = D_MMAP_ANON,
};
-static void *zbuf;
-
/* ARGSUSED */
static int
null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
@@ -95,10 +93,19 @@ null_ioctl(struct cdev *dev __unused, u_
static int
zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
{
+ void *zbuf;
+ ssize_t len;
int error = 0;
- while (uio->uio_resid > 0 && error == 0)
- error = uiomove(zbuf, MIN(uio->uio_resid, PAGE_SIZE), uio);
+ KASSERT(uio->uio_rw == UIO_READ,
+ ("Can't be in %s for write", __func__));
+ zbuf = __DECONST(void *, zero_region);
+ while (uio->uio_resid > 0 && error == 0) {
+ len = uio->uio_resid;
+ if (len > ZERO_REGION_SIZE)
+ len = ZERO_REGION_SIZE;
+ error = uiomove(zbuf, len, uio);
+ }
return (error);
}
@@ -111,7 +118,6 @@ null_modevent(module_t mod __unused, int
case MOD_LOAD:
if (bootverbose)
printf("null: <null device, zero device>\n");
- zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK | M_ZERO);
null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
NULL, UID_ROOT, GID_WHEEL, 0666, "null");
zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
@@ -121,7 +127,6 @@ null_modevent(module_t mod __unused, int
case MOD_UNLOAD:
destroy_dev(null_dev);
destroy_dev(zero_dev);
- free(zbuf, M_TEMP);
break;
case MOD_SHUTDOWN:
Modified: head/sys/sys/systm.h
==============================================================================
--- head/sys/sys/systm.h Fri May 13 18:46:20 2011 (r221852)
+++ head/sys/sys/systm.h Fri May 13 18:48:00 2011 (r221853)
@@ -125,6 +125,9 @@ extern char static_hints[]; /* by config
extern char **kenvp;
+extern const void *zero_region; /* address space maps to a zeroed page
*/
+#define ZERO_REGION_SIZE (2048 * 1024)
+
/*
* General function declarations.
*/
Modified: head/sys/vm/vm_kern.c
==============================================================================
--- head/sys/vm/vm_kern.c Fri May 13 18:46:20 2011 (r221852)
+++ head/sys/vm/vm_kern.c Fri May 13 18:48:00 2011 (r221853)
@@ -91,6 +91,9 @@ vm_map_t exec_map=0;
vm_map_t pipe_map;
vm_map_t buffer_map=0;
+const void *zero_region;
+CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
+
/*
* kmem_alloc_nofault:
*
@@ -527,6 +530,35 @@ kmem_free_wakeup(map, addr, size)
vm_map_unlock(map);
}
+static void
+kmem_init_zero_region(void)
+{
+ vm_offset_t addr;
+ vm_page_t m;
+ unsigned int i;
+ int error;
+
+ /* Allocate virtual address space. */
+ addr = kmem_alloc_nofault(kernel_map, ZERO_REGION_SIZE);
+
+ /* Allocate a page and zero it. */
+ m = vm_page_alloc(NULL, OFF_TO_IDX(addr - VM_MIN_KERNEL_ADDRESS),
+ VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
+ if ((m->flags & PG_ZERO) == 0)
+ pmap_zero_page(m);
+
+ /* Map the address space to the page. */
+ for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
+ pmap_qenter(addr + i, &m, 1);
+
+ /* Protect it r/o. */
+ error = vm_map_protect(kernel_map, addr, addr + ZERO_REGION_SIZE,
+ VM_PROT_READ, TRUE);
+ KASSERT(error == 0, ("error=%d", error));
+
+ zero_region = (const void *)addr;
+}
+
/*
* kmem_init:
*
@@ -555,6 +587,8 @@ kmem_init(start, end)
start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
/* ... and ending with the completion of the above `insert' */
vm_map_unlock(m);
+
+ kmem_init_zero_region();
}
#ifdef DIAGNOSTIC
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