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tcp.7: Document removal of TCP_SYNQ_HSIZE 

Looking over the man page for 'tcp' I came across a reference to
tuning the 'TCP_SYNQ_HSIZE' parameter when increasing
'tcp_max_syn_backlog' above 1024. However, this static sizing was
removed back in Linux 2.6.20 in favor of dynamic scaling - as
part of commit 72a3effaf633bcae9034b7e176bdbd78d64a71db.

I have included a patch below with reference to this commit, and
that the process detailed is not required on >= Linux 2.6.20.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Peter Adkins 2015-03-12 00:15:12 -07:00 committed by Michael Kerrisk
parent 75295d40e4
commit 09fe692d1b
1 changed files with 7 additions and 3 deletions
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man7/tcp.7
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@ -530,12 +530,16 @@ The default value of 256 is increased to
1024 when the memory present in the system is adequate or
greater (>= 128Mb), and reduced to 128 for those systems with
very low memory (<= 32Mb).
It is recommended that if this
needs to be increased above 1024, TCP_SYNQ_HSIZE in
Prior to Linux 2.6.20,
.\" commit 72a3effaf633bcae9034b7e176bdbd78d64a71db
it was recommended that if this needed to be increased above 1024,
the size of the SYNACK hash table (TCP_SYNQ_HSIZE) in
.I include/net/tcp.h
be modified to keep
TCP_SYNQ_HSIZE*16<=tcp_max_syn_backlog, and the kernel be
recompiled.
recompiled. In Linux 2.6.20, the fixed sized TCP_SYNQ_HSIZE was removed
in favour of dynamic sizing.
.TP
.IR tcp_max_tw_buckets " (integer; default: see below; since Linux 2.4)"
.\" Since 2.3.41