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tcp.7: Update description of tcp_rmem defaults for Linux 2.6 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2008-11-21 16:59:23 -05:00
parent 412a6fd924
commit 48a2a0bf5b
1 changed files with 11 additions and 6 deletions
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17
man7/tcp.7
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@ -583,9 +583,10 @@ of these values, depending on memory available in the system.
.TP 9
.I min
minimum size of the receive buffer used by each TCP socket.
The default value is 4K, and is lowered to
The default value is the system page size.
(On Linux 2.4, the default value is 4K, lowered to
.B PAGE_SIZE
bytes in low-memory systems.
bytes in low-memory systems.)
This value
is used to ensure that in memory pressure mode,
allocations below this size will still succeed.
@ -601,8 +602,8 @@ This value overwrites the initial default buffer size from
the generic global
.I net.core.rmem_default
defined for all protocols.
The default value is 87380
bytes, and is lowered to 43689 in low-memory systems.
The default value is 87380 bytes.
(In Linux 2.4, this will be lowered to 43689 in low-memory systems.)
If larger receive buffer sizes are desired, this value should
be increased (to affect all sockets).
To employ large TCP windows, the
@ -616,8 +617,12 @@ This value does not override the global
This is not used to limit the size of the receive buffer declared using
.B SO_RCVBUF
on a socket.
The default value of 87380*2 bytes is lowered to 87380
in low-memory systems.
The default value is the calculates using the formula
max(87380, min(4MB, \fItcp_mem\fP[1]*PAGE_SIZE/128))
(On Linux 2.4, the default is 87380*2 bytes,
lowered to 87380 in low-memory systems).
.RE
.TP
.IR tcp_sack " (Boolean; default: enabled; since Linux 2.2)"