In Linux versions before 2.6.11, the capacity of a pipe was the same as the system page size (e.g., 4096 bytes on i386). Since Linux 2.6.11, the pipe capacity is 16 pages (i.e., 65,536 bytes in a system with a page size of 4096 bytes). Since Linux 2.6.35, the default pipe capacity is 16 pages, but the capacity can be queried and set using the fcntl(2) F_GETPIPE_SZ and F_SETPIPE_SZ operations.
Change the capacity of the pipe referred to by fd to be at least arg bytes. An unprivileged process can adjust the pipe capacity to any value between the
system page size and the limit defined in /proc/sys/fs/pipe-max-size (see proc(5)). Attempts to set the pipe capacity below the page size are silently
rounded up to the page size. Attempts by an unprivileged process to set the pipe capacity above the limit in /proc/sys/fs/pipe-max-size yield the error
EPERM; a privileged process (CAP_SYS_RESOURCE) can override the limit.
When allocating the buffer for the pipe, the kernel may use a capacity larger than arg, if that is convenient for the implementation. (In the current
implementation, the allocation is the next higher power-of-two page-size multiple of the requested size.) The actual capacity (in bytes) that is set is
returned as the function result.
Attempting to set the pipe capacity smaller than the amount of buffer space currently used to store data produces the error EBUSY.
F_GETPIPE_SZ (void; since Linux 2.6.35)
Return (as the function result) the capacity of the pipe referred to by fd.
To validate this let us create a fifo pipe file
Next below python script (/tmp/change_fifo_size.py) can be used to get the default size and also to increase the pipe buffer size to any new value
F_SETPIPE_SZ = 1031 # Linux 2.6.35+
F_GETPIPE_SZ = 1032 # Linux 2.6.35+
print "Checking fifo file ..."
fifo_fd = open(fifo, "rb+")
print "Pipe size : "+str(fcntl.fcntl(fifo_fd, F_GETPIPE_SZ))
fcntl.fcntl(fifo_fd, F_SETPIPE_SZ, 1000000)
print "Pipe (modified) size : "+str(fcntl.fcntl(fifo_fd, F_GETPIPE_SZ))
except Exception, e:
print "Unable to create fifo, error: "+str(e)
fifo_fd = open_fifo("/tmp/testfifo")
Here you can replace the highlighted sections as per your requirement i.e. the location and size of the pipe file
Execute the above script
Checking fifo file ....
Pipe size : 65536
Pipe (modified) size : 1048576
So the default fifo file size was 64KB which is increased to 1MB.
I hope the article was useful.