pipe.7: Clarify that default pipe capacity is 16 pages

The statement that the default pipe capacity is 65536 bytes
is accurate only on systems where the page size is 4096B.
See the use of PIPE_DEF_BUFFERS in the kernel source.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/pipe.7 b/man7/pipe.7
index 3df4e08669bd63747cd85cbd62715a1a2aebaed0..cff9b75e928b585dff640118107ced3f7258d06f 100644 (file)
--- a/man7/pipe.7
+++ b/man7/pipe.7
@@ -132,8 +132,9 @@ so that a writing process does not remain blocked.
 
 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 65536 bytes.
-Since Linux 2.6.35, the default pipe capacity is 65536 bytes,
+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
 .BR fcntl (2)
 .BR F_GETPIPE_SZ