mirror of https://github.com/mkerrisk/man-pages
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>
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@ -530,12 +530,16 @@ The default value of 256 is increased to
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1024 when the memory present in the system is adequate or
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1024 when the memory present in the system is adequate or
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greater (>= 128Mb), and reduced to 128 for those systems with
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greater (>= 128Mb), and reduced to 128 for those systems with
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very low memory (<= 32Mb).
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very low memory (<= 32Mb).
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It is recommended that if this
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needs to be increased above 1024, TCP_SYNQ_HSIZE in
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Prior to Linux 2.6.20,
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.\" commit 72a3effaf633bcae9034b7e176bdbd78d64a71db
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it was recommended that if this needed to be increased above 1024,
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the size of the SYNACK hash table (TCP_SYNQ_HSIZE) in
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.I include/net/tcp.h
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.I include/net/tcp.h
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be modified to keep
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be modified to keep
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TCP_SYNQ_HSIZE*16<=tcp_max_syn_backlog, and the kernel be
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TCP_SYNQ_HSIZE*16<=tcp_max_syn_backlog, and the kernel be
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recompiled.
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recompiled. In Linux 2.6.20, the fixed sized TCP_SYNQ_HSIZE was removed
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in favour of dynamic sizing.
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.TP
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.TP
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.IR tcp_max_tw_buckets " (integer; default: see below; since Linux 2.4)"
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.IR tcp_max_tw_buckets " (integer; default: see below; since Linux 2.4)"
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.\" Since 2.3.41
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.\" Since 2.3.41
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