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43 .Nd lightweight buffers
47 .Fn lwbuf_alloc "vm_page_t m" "struct lwbuf *"
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 argument is an lwbuf structure, used to avoid allocation of an lwbuf
69 on the x86_64 architecture. The
71 argument is unused on the i386 architecture.
74 frees all resources associated with the lightweight buffer
84 of the lightweight buffer
90 previously obtained through
92 will be valid on all processors without subsequent calls to
94 It should not be used.
95 .Sh IMPLEMENTATION NOTES
99 On i386, pages taken from
100 per-processor pools of kernel virtual address space (KVA) are used to map
104 On x86_64 such tricks are unnecessary, the
105 kernel maintains a direct map of KVA covering all physical memory.
107 Lightweight buffers are thread and cross-processor safe with a number of
109 Allocated buffers are not internally cached or reference counted.
110 Any consumer of lightweight buffers may elect to share allocated buffers
111 or allow them to be used in other threads or on other processors, but care
113 Buffers must be externally refcounted or in some other manner
114 freed only after last use.
118 implementation first appeared in
123 implementation and this manpage were written by
124 .An Samuel J. Greear .