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
This commit is contained in:
parent
14f9771b27
commit
89cb2a19ec
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=221853
@ -205,9 +205,6 @@ struct md_s {
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vm_object_t object;
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};
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/* Used for BIO_DELETE on MD_VNODE */
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static u_char zero[PAGE_SIZE];
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static struct indir *
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new_indir(u_int shift)
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{
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@ -560,7 +557,8 @@ mdstart_vnode(struct md_s *sc, struct bio *bp)
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* that the two cases end up having very little in common.
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*/
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if (bp->bio_cmd == BIO_DELETE) {
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zerosize = sizeof(zero) - (sizeof(zero) % sc->sectorsize);
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zerosize = ZERO_REGION_SIZE -
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(ZERO_REGION_SIZE % sc->sectorsize);
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auio.uio_iov = &aiov;
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auio.uio_iovcnt = 1;
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auio.uio_offset = (vm_ooffset_t)bp->bio_offset;
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@ -573,7 +571,7 @@ mdstart_vnode(struct md_s *sc, struct bio *bp)
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vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
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error = 0;
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while (auio.uio_offset < end) {
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aiov.iov_base = zero;
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aiov.iov_base = __DECONST(void *, zero_region);
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aiov.iov_len = end - auio.uio_offset;
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if (aiov.iov_len > zerosize)
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aiov.iov_len = zerosize;
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@ -65,8 +65,6 @@ static struct cdevsw zero_cdevsw = {
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.d_flags = D_MMAP_ANON,
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};
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static void *zbuf;
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/* ARGSUSED */
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static int
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null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
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@ -95,10 +93,19 @@ null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
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static int
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zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
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{
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void *zbuf;
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ssize_t len;
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int error = 0;
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while (uio->uio_resid > 0 && error == 0)
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error = uiomove(zbuf, MIN(uio->uio_resid, PAGE_SIZE), uio);
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KASSERT(uio->uio_rw == UIO_READ,
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("Can't be in %s for write", __func__));
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zbuf = __DECONST(void *, zero_region);
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while (uio->uio_resid > 0 && error == 0) {
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len = uio->uio_resid;
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if (len > ZERO_REGION_SIZE)
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len = ZERO_REGION_SIZE;
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error = uiomove(zbuf, len, uio);
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}
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return (error);
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}
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@ -111,7 +118,6 @@ null_modevent(module_t mod __unused, int type, void *data __unused)
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case MOD_LOAD:
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if (bootverbose)
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printf("null: <null device, zero device>\n");
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zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK | M_ZERO);
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null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
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NULL, UID_ROOT, GID_WHEEL, 0666, "null");
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zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
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@ -121,7 +127,6 @@ null_modevent(module_t mod __unused, int type, void *data __unused)
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case MOD_UNLOAD:
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destroy_dev(null_dev);
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destroy_dev(zero_dev);
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free(zbuf, M_TEMP);
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break;
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case MOD_SHUTDOWN:
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@ -125,6 +125,9 @@ extern char static_hints[]; /* by config for now */
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extern char **kenvp;
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extern const void *zero_region; /* address space maps to a zeroed page */
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#define ZERO_REGION_SIZE (2048 * 1024)
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/*
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* General function declarations.
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*/
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@ -91,6 +91,9 @@ vm_map_t exec_map=0;
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vm_map_t pipe_map;
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vm_map_t buffer_map=0;
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const void *zero_region;
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CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
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/*
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* kmem_alloc_nofault:
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*
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@ -527,6 +530,35 @@ kmem_free_wakeup(map, addr, size)
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vm_map_unlock(map);
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}
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static void
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kmem_init_zero_region(void)
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{
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vm_offset_t addr;
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vm_page_t m;
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unsigned int i;
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int error;
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/* Allocate virtual address space. */
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addr = kmem_alloc_nofault(kernel_map, ZERO_REGION_SIZE);
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/* Allocate a page and zero it. */
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m = vm_page_alloc(NULL, OFF_TO_IDX(addr - VM_MIN_KERNEL_ADDRESS),
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VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
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if ((m->flags & PG_ZERO) == 0)
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pmap_zero_page(m);
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/* Map the address space to the page. */
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for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
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pmap_qenter(addr + i, &m, 1);
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/* Protect it r/o. */
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error = vm_map_protect(kernel_map, addr, addr + ZERO_REGION_SIZE,
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VM_PROT_READ, TRUE);
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KASSERT(error == 0, ("error=%d", error));
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zero_region = (const void *)addr;
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}
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/*
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* kmem_init:
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*
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@ -555,6 +587,8 @@ kmem_init(start, end)
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start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
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/* ... and ending with the completion of the above `insert' */
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vm_map_unlock(m);
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kmem_init_zero_region();
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}
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#ifdef DIAGNOSTIC
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