Hi, the patch at http://www.trematerra.net/patches/pipefifo_merge2.diff

is a preliminary version of the FIFO optimizations project that I picked up from the wiki. http://wiki.freebsd.org/IdeasPage#FIFO_optimizations_.28GSoC.29

zhaoshuai@ produced the following patch in the 2009 which attempted a first merge of the interfaces: http://www.trematerra.net/patches/fifo_soc2009.diff

However I felt like the work was not yet completed and come up with my final version. Now fifoes derive their structures from pipes one with just special handling to support VFS operations. All the operations but the creation/destruction for fifoes and pipes are handled by the same code. The heart of the patch is the new struct pipeinfo. pipeinfo is a per-file descriptor state. Basically it maintains a read end and a write end for the descriptor. As pipes are bidirectional in FreeBSD, for a pipe this two fields are always equal but different for a fifo. To let fifo code in sys/fs/fifofs/fifo_vnops.c create/destroy the pipe, two functions (pipe_ctor/pipe_dtor) were written. pipe_ctor setups things like a call to kern_pipe and return a pipeinfo structure, while pipe_dtor releases all the resources for a given pipeinfo. Once a pipe was setup during a fifo_open call, all the subsequent operations on the fifo are handled by the same code of a pipe expect for the clean up code that calls pipe_dtor. Allocation of two pipeinfo structures for a pipe were showed to slow down things by some micro-benchmarking. To speed up things during creation/destruction of pipes, the patch allocates all the needed data structure zone using the umapipe struct that packing together all the needed data structures to be allocated at pipe creation. A similar umafifo structure is used for fifoes. Thanks to jilles that made a review of the patch in a previous form, privately. Thanks a lot to attilio that answered my stupid questions and drove me in the right direction.