File: document-buffer-limits

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buffer 1.19-12
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--- a/buffer.man
+++ b/buffer.man
@@ -130,6 +130,25 @@
 $ \fBtar cf - . | buffer | 
 .br
 \ \ \ rsh somehost 'buffer -S 500K -p 75 > /dev/rst0'\fP
+.SH BUFFER LIMITS
+There are 2 limits in
+.I buffer
+affecting the maximum total buffer size: The maximum number of blocks (2048)
+and the maximum size of a block (512kB). This results in a maximum total
+buffer size of 1GB.
+.PP
+
+Note that there is also a kernel limit for the maximum size of a shared
+memory segment (used by
+.I buffer
+internally) which is typically much lower than the limits in
+.IR buffer .
+So if
+.I buffer
+complains about not being able to create a shared memory segment, this limit
+might have to be raised using the command \fBsysctl kernel.shmmax=\fP\fIXXX\fP (see also
+sysctl(1) and proc(5)).
+
 .SH BUGS
 Internally, for printing purposes, buffer counts in terms of the
 number of kilobytes output.  If the blocksize you use is not a whole