diff --git a/man7/tcp.7 b/man7/tcp.7 index 1afb8aa36..205b03e72 100644 --- a/man7/tcp.7 +++ b/man7/tcp.7 @@ -485,23 +485,25 @@ available memory. .I "low memory" for this, which is limited to around 900 megabytes on 32-bit systems. 64-bit systems do not suffer this limitation.) - +.RS +.TP 10 .I low -- TCP doesn't regulate its memory allocation when the number +TCP doesn't regulate its memory allocation when the number of pages it has allocated globally is below this number. - +.TP .I pressure -- when the amount of memory allocated by TCP +When the amount of memory allocated by TCP exceeds this number of pages, TCP moderates its memory consumption. This memory pressure state is exited once the number of pages allocated falls below the .I low mark. - +.TP .I high -- the maximum number of pages, globally, that TCP will allocate. +The maximum number of pages, globally, that TCP will allocate. This value overrides any other limits imposed by the kernel. +.RE .TP .IR tcp_mtu_probing " (integer; default: 0; since Linux 2.6.17)" .\" The following is from 2.6.28-rc4: Documentation/networking/ip-sysctl.txt @@ -582,7 +584,7 @@ TCP dynamically adjusts the size of the receive buffer from the defaults listed below, in the range of these values, depending on memory available in the system. .RS -.TP 9 +.TP 10 .I min minimum size of the receive buffer used by each TCP socket. The default value is the system page size. @@ -757,9 +759,10 @@ These parameters are used by TCP to regulate send buffer sizes. TCP dynamically adjusts the size of the send buffer from the default values listed below, in the range of these values, depending on memory available. - +.RS +.TP 10 .I min -- minimum size of the send buffer used by each TCP socket. +Minimum size of the send buffer used by each TCP socket. The default value is the system page size. (On Linux 2.4, the default value is 4K bytes.) This value is used to ensure that in memory pressure mode, @@ -767,9 +770,9 @@ allocations below this size will still succeed. This is not used to bound the size of the send buffer declared using .B SO_SNDBUF on a socket. - +.TP .I default -- the default size of the send buffer for a TCP socket. +The default size of the send buffer for a TCP socket. This value overwrites the initial default buffer size from the generic global .I net.core.wmem_default @@ -781,9 +784,9 @@ should be increased (to affect all sockets). To employ large TCP windows, the .I /proc/sys/net/ipv4/tcp_window_scaling must be set to a non-zero value (default). - +.TP .I max -- the maximum size of the send buffer used by each TCP socket. +The maximum size of the send buffer used by each TCP socket. This value does not override the value in .IR /proc/sys/net/core/wmem_max . This is not used to limit the size of the send buffer declared using @@ -795,6 +798,7 @@ The default value is calculated using the formula (On Linux 2.4, the default value is 128K bytes, lowered 64K depending on low-memory systems.) +.RE .TP .IR tcp_workaround_signed_windows " (Boolean; default: disabled; since Linux 2.6.26)" If enabled, assume that no receipt of a window-scaling option means that the