Please send me your comments to
- Ulisses Alonso Camaró <uaca@i.hate.spam.alumni.uv.es>
+ Ulisses Alonso Camaró <uaca@i.hate.spam.alumni.uv.es>
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+ Why use PACKET_MMAP
block #1
-kmalloc allocates any number of bytes of phisically contiguous memory from
-a pool of pre-determined sizes. This pool of memory is mantained by the slab
+kmalloc allocates any number of bytes of physically contiguous memory from
+a pool of pre-determined sizes. This pool of memory is maintained by the slab
allocator which is at the end the responsible for doing the allocation and
hence which imposes the maximum memory that kmalloc can allocate.
All memory allocations are not freed until the socket is closed. The memory
allocations are done with GFP_KERNEL priority, this basically means that
the allocation can wait and swap other process' memory in order to allocate
-the nececessary memory, so normally limits can be reached.
+the necessary memory, so normally limits can be reached.
Other constraints
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If you check the source code you will see that what I draw here as a frame
-is not only the link level frame. At the begining of each frame there is a
+is not only the link level frame. At the beginning of each frame there is a
header called struct tpacket_hdr used in PACKET_MMAP to hold link level's frame
meta information like timestamp. So what we draw here a frame it's really
the following (from include/linux/if_packet.h):