[PATCH] IO#syswrite releases GVL
ruby 1.9.3dev (2011-03-25 trunk 31173) [x86_64-linux]
2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
While local FS writes are usually buffered, the buffers can be
full or the file opened with O_SYNC. IO#syswrite can also be
used on blocking IOs (pipe/socket) just like IO#write.