From: Eric Dumazet <dada1@cosmosbay.com>
Date: Tue, 27 Jan 2009 05:35:35 +0000 (-0800)
Subject: udp: optimize bind(0) if many ports are in use
X-Git-Tag: v2.6.29-rc4~91^2~22
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=98322f22eca889478045cf896b572250d03dc45f;p=pandora-kernel.git

udp: optimize bind(0) if many ports are in use

commit 9088c5609584684149f3fb5b065aa7f18dcb03ff
(udp: Improve port randomization) introduced a regression for UDP bind() syscall
to null port (getting a random port) in case lot of ports are already in use.

This is because we do about 28000 scans of very long chains (220 sockets per chain),
with many spin_lock_bh()/spin_unlock_bh() calls.

Fix this using a bitmap (64 bytes for current value of UDP_HTABLE_SIZE)
so that we scan chains at most once.

Instead of 250 ms per bind() call, we get after patch a time of 2.9 ms

Based on a report from Vitaly Mayatskikh

Reported-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Tested-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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