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43 .Nd "Lightweight buffers"
47 .Fn lwbuf_alloc "vm_page_t m"
49 .Fn lwbuf_free "struct lwbuf *lwb"
51 .Fn lwbuf_page "struct lwbuf *lwb"
53 .Fn lwbuf_kva "struct lwbuf *lwb"
55 .Fn lwbuf_set_global "struct lwbuf *lwb"
59 kernel functions are used for maintaining a lightweight reference to and
60 accessing an arbitrary
64 returns a pointer to a lightweight buffer representing
68 frees all resources associated with the lightweight buffer
78 of the lightweight buffer
82 ensures that a vm_offset_t previously obtained through
84 will be valid on all processors without subsequent calls to
86 It should not be used.
87 .Sh IMPLEMENTATION NOTES
90 is cpu-dependent. On i386, pages taken from
91 per-processor pools of kernel virtual address space (KVA) are used to map
94 objects. On x86_64 such tricks are unnecessary, the
95 kernel maintains a direct map of KVA covering all physical memory.
97 Lightweight buffers are thread and cross-processor safe with a number of
98 limitations. Allocated buffers are not internally cached or reference counted.
99 Any consumer of lightweight buffers may elect to share allocated buffers
100 or allow them to be used in other threads or on other processors, but care
101 must be taken. Buffers must be externally refcounted or in some other manner
102 freed only after last use.
106 implementation first appeared in
111 implementation and this manpage were written by
112 .An Samuel J. Greear .