How can I properly create a write buffer? Currently, I am using a linked list of allocated buffers but most of by writes are only a few bytes. What are your suggestions on creating an efficient write buffer?
Linked list is probably not the best choice here. Its traversal is not cache friendly and thus is expensive.
You can use a ring buffer [1], some consumer will put raw bytes into it and some producer will later grab the whole available content and send it in one syscall.
If writing to a continuous memory region is not desirable (e.g. you can't do it in zero-copy fashion), you can put struct iovec referencing your memory into the ring buffer. Consumer will then grab all iovec's and pass them to writev [2].
Speaking of producers and consumers, they might be OS level threads, and you will have to synchronize them around you buffer, or they might be fibers [3]. The latter is preferable if you are doing an event driven application. I have an implementation [4] of fibers specifically for libev that you can look at. Also it includes efficient virtual ring buffer implementation.
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