Documentation: clarify tcp_{r,w}mem sysctl docs

Fix some of the defaults and attempt to clarify some language.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 11 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 277437951e4d..dc04fdd6af34 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -336,7 +336,7 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
         pressure.
         Default: 8K
 
-        default: default size of receive buffer used by TCP sockets.
+        default: initial size of receive buffer used by TCP sockets.
         This value overrides net.core.rmem_default used by other protocols.
         Default: 87380 bytes. This value results in window of 65535 with
         default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
@@ -344,8 +344,10 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
 
         max: maximal size of receive buffer allowed for automatically
         selected receiver buffers for TCP socket. This value does not override
-        net.core.rmem_max, "static" selection via SO_RCVBUF does not use this.
-        Default: 87380*2 bytes.
+        net.core.rmem_max.  Calling setsockopt() with SO_RCVBUF disables
+        automatic tuning of that socket's receive buffer size, in which
+        case this value is ignored.
+        Default: between 87380B and 4MB, depending on RAM size.
 
 tcp_sack - BOOLEAN
         Enable select acknowledgments (SACKS).
@@ -419,19 +421,21 @@ tcp_window_scaling - BOOLEAN
         Enable window scaling as defined in RFC1323.
 
 tcp_wmem - vector of 3 INTEGERs: min, default, max
-        min: Amount of memory reserved for send buffers for TCP socket.
+        min: Amount of memory reserved for send buffers for TCP sockets.
         Each TCP socket has rights to use it due to fact of its birth.
         Default: 4K
 
-        default: Amount of memory allowed for send buffers for TCP socket
-        by default. This value overrides net.core.wmem_default used
-        by other protocols, it is usually lower than net.core.wmem_default.
+        default: initial size of send buffer used by TCP sockets.  This
+        value overrides net.core.wmem_default used by other protocols.
+        It is usually lower than net.core.wmem_default.
         Default: 16K
 
-        max: Maximal amount of memory allowed for automatically selected
-        send buffers for TCP socket. This value does not override
-        net.core.wmem_max, "static" selection via SO_SNDBUF does not use this.
-        Default: 128K
+        max: Maximal amount of memory allowed for automatically tuned
+        send buffers for TCP sockets. This value does not override
+        net.core.wmem_max.  Calling setsockopt() with SO_SNDBUF disables
+        automatic tuning of that socket's send buffer size, in which case
+        this value is ignored.
+        Default: between 64K and 4MB, depending on RAM size.
 
 tcp_workaround_signed_windows - BOOLEAN
         If set, assume no receipt of a window scaling option means the