| buf.9 (3a858f3798eb709b5f316cdae50865332284211d) | buf.9 (d5a8819cb767682dbed8b6bd75a68f382c297603) |
|---|---|
| 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. --- 111 unchanged lines hidden (view full) --- 120device no longer needs a buffer it typically flags it as B_RELBUF. 121Due to 122the underlying pages being marked clean, the B_DELWRI|B_RELBUF combination must 123be interpreted to mean that the buffer is still actually dirty and must be 124written to its backing store before it can actually be released. 125In the case 126where B_DELWRI is not set, the underlying dirty pages are still properly 127marked as dirty and the buffer can be completely freed without losing that | 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. --- 111 unchanged lines hidden (view full) --- 120device no longer needs a buffer it typically flags it as B_RELBUF. 121Due to 122the underlying pages being marked clean, the B_DELWRI|B_RELBUF combination must 123be interpreted to mean that the buffer is still actually dirty and must be 124written to its backing store before it can actually be released. 125In the case 126where B_DELWRI is not set, the underlying dirty pages are still properly 127marked as dirty and the buffer can be completely freed without losing that |
| 128clean/dirty state information. ( XXX do we have to check other flags in 129regards to this situation ??? ). | 128clean/dirty state information. 129.Po 130XXX do we have to check other flags in 131regards to this situation ??? 132.Pc |
| 130.Pp 131The kernel reserves a portion of its KVM space to hold VM Buffer's data 132maps. 133Even though this is virtual space (since the buffers are mapped 134from the buffer cache), we cannot make it arbitrarily large because 135instantiated VM Buffers (struct buf's) prevent their underlying pages in the 136buffer cache from being freed. 137This can complicate the life of the paging --- 12 unchanged lines hidden --- | 133.Pp 134The kernel reserves a portion of its KVM space to hold VM Buffer's data 135maps. 136Even though this is virtual space (since the buffers are mapped 137from the buffer cache), we cannot make it arbitrarily large because 138instantiated VM Buffers (struct buf's) prevent their underlying pages in the 139buffer cache from being freed. 140This can complicate the life of the paging --- 12 unchanged lines hidden --- |