Messages in this thread | | | Date | Tue, 12 Jul 2005 16:55:10 -0700 | From | Andrew Morton <> | Subject | Re: Merging relayfs? |
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Steven Rostedt <rostedt@goodmis.org> wrote: > > I will also admit that my ring buffers lost one byte per page. Because > I wanted to save on space with the accounting, and only had a start and > end pointer per page. So when start and end were equal, the buffer was > considered empty and when end was one less than start, it was considered > full. But since end always pointed to an empty spot, it would still be > empty when the buffer was full, thus wasting one byte per page. But to > solve this, I would either have to add another variable in the buffer > page descriptor (adding at least one byte, but probably 4 bytes) which > would just be more waste, or I would have to make a complex system even > more complex (ie. adding a flag on the end pointer at the MSB to > differentiate between end being empty or filled).
Nope. Just make the indices 32-bit numbers and let them wrap.
Full: (tail - head) == size Empty: (tail - head) == 0 Add item: buf[head++ & (size-1)] = item; Remove item: buf[tail++ & (size-1)] - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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