Date: Tue, 1 Apr 2008 11:41:29 +0100 From: Rui Paulo <rpaulo@FreeBSD.org> To: Anthony Pankov <ap00@mail.ru> Cc: freebsd-net@freebsd.org, performance@freebsd.org Subject: Re: packet delay because of blackhole Message-ID: <20080401104128.GA1194@fnop.net> In-Reply-To: <1333421734.20080328201458@mail.ru> References: <1333421734.20080328201458@mail.ru>
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On Fri, Mar 28, 2008 at 08:14:58PM +0300, Anthony Pankov wrote: > Just for somebody convince. > > While analyzing client<->server HTTPS conversation one second delay in > packet exchange was discovered (strongly reproducible): > > Sample: > N time > 6 0.002303 10.28.4.14 10.28.4.50 SSL Client Hello > 7 0.106710 10.28.4.50 10.28.4.14 TCP 443 > 1447 [ACK] Seq=1 Ack=103 Win=65535 Len=0 > 8 1.045712 10.28.4.50 10.28.4.14 TLSv1 Server Hello, Certificate, Server Hello Done > > Another sample: > 10 0.011722 10.28.4.14 10.28.4.50 TLSv1 Application Data > 11 0.115933 10.28.4.50 10.28.4.14 TCP 443 > 1442 [ACK] Seq=839 Ack=519 Win=65466 Len=0 > 12 1.054037 10.28.4.50 10.28.4.14 TLSv1 Application Data > > The reason for delay is sysctl tcp.blackhole value grater than 0, much to surprise. > > So, turning tcp.blackhole to 0 eliminate any delay (strongly reproducible). > > System: FreeBSD 6_2_stable I'm not sure how performance penalty can induce a cache miss and I it's very processor specific. So, you're best guess is to profile the kernel. Regards, -- Rui Paulo
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