Date: Fri, 13 May 2011 18:48:01 +0000 (UTC) From: Matthew D Fleming <mdf@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r221853 - in head/sys: dev/md dev/null sys vm Message-ID: <201105131848.p4DIm1j7079495@svn.freebsd.org>
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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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