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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 1024 when the memory present in the system is adequate or
greater (>= 128Mb), and reduced to 128 for those systems with greater (>= 128Mb), and reduced to 128 for those systems with
very low memory (<= 32Mb). 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 .I include/net/tcp.h
be modified to keep be modified to keep
TCP_SYNQ_HSIZE*16<=tcp_max_syn_backlog, and the kernel be 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 .TP
.IR tcp_max_tw_buckets " (integer; default: see below; since Linux 2.4)" .IR tcp_max_tw_buckets " (integer; default: see below; since Linux 2.4)"
.\" Since 2.3.41 .\" Since 2.3.41