| buf.9 (88b85f7467f06bac27e50e664da04aed9ecb9929) | buf.9 (a04dd7481b80786760f38ff3902e24851fc7ef37) |
|---|---|
| 1.\" Copyright (c) 1998 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 15 unchanged lines hidden (view full) --- 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" | 1.\" Copyright (c) 1998 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 15 unchanged lines hidden (view full) --- 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" |
| 32.\" $Id: security.7,v 1.1 1998/12/20 20:12:17 dillon Exp $ | 32.\" $Id: buf.9,v 1.1 1998/12/22 19:47:48 dillon Exp $ |
| 33.\" 34.Dd December 22, 1998 35.Dt BUF 9 36.Os 37.Sh NAME 38.Nm BUF/BP 39.Nd Kernel Buffer I/O scheme used in FreeBSD VM system 40.Sh DESCRIPTION --- 14 unchanged lines hidden (view full) --- 55mapping, the b_data base pointer in a buf is always *page* aligned, not 56*block* aligned. When you have a VM buffer representing some b_offset and 57b_size, the actual start of the buffer is (b_data + (b_offset & PAGE_MASK)) 58and not just b_data. Finally, the VM system's core buffer cache supports 59valid and dirty bits (m->valid, m->dirty) for pages in DEV_BSIZE chunks. Thus 60a platform with a hardware page size of 4096 bytes has 8 valid and 8 dirty 61bits. These bits are generally set and cleared in groups based on the device 62block size of the device backing the page. Complete page's worth are often | 33.\" 34.Dd December 22, 1998 35.Dt BUF 9 36.Os 37.Sh NAME 38.Nm BUF/BP 39.Nd Kernel Buffer I/O scheme used in FreeBSD VM system 40.Sh DESCRIPTION --- 14 unchanged lines hidden (view full) --- 55mapping, the b_data base pointer in a buf is always *page* aligned, not 56*block* aligned. When you have a VM buffer representing some b_offset and 57b_size, the actual start of the buffer is (b_data + (b_offset & PAGE_MASK)) 58and not just b_data. Finally, the VM system's core buffer cache supports 59valid and dirty bits (m->valid, m->dirty) for pages in DEV_BSIZE chunks. Thus 60a platform with a hardware page size of 4096 bytes has 8 valid and 8 dirty 61bits. These bits are generally set and cleared in groups based on the device 62block size of the device backing the page. Complete page's worth are often |
| 63refered to using the VM_PAGE_BITS_ALL bitmask (i.e. 0xFF if the hardware page | 63referred to using the VM_PAGE_BITS_ALL bitmask (i.e. 0xFF if the hardware page |
| 64size is 4096). 65.Pp 66VM buffers also keep track of a byte-granular dirty range and valid range. 67This feature is normally only used by the NFS subsystem. I'm not sure why it 68is used at all, actually, since we have DEV_BSIZE valid/dirty granularity 69within the VM buffer. If a buffer dirty operation creates a 'hole', 70the dirty range will extend to cover the hole. If a buffer validation 71operation creates a 'hole' the byte-granular valid range is left alone and --- 52 unchanged lines hidden --- | 64size is 4096). 65.Pp 66VM buffers also keep track of a byte-granular dirty range and valid range. 67This feature is normally only used by the NFS subsystem. I'm not sure why it 68is used at all, actually, since we have DEV_BSIZE valid/dirty granularity 69within the VM buffer. If a buffer dirty operation creates a 'hole', 70the dirty range will extend to cover the hole. If a buffer validation 71operation creates a 'hole' the byte-granular valid range is left alone and --- 52 unchanged lines hidden --- |