Date: Thu, 6 Nov 2014 12:00:49 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Matthew Seaman <matthew@freebsd.org> Cc: freebsd-stable@freebsd.org, Steven Hartland <killing@multiplay.co.uk> Subject: Re: Varnish proxy goes catatonic under heavy load Message-ID: <20141106100049.GO53947@kib.kiev.ua> In-Reply-To: <545B4310.7000403@freebsd.org> References: <545A0EB4.4090404@freebsd.org> <545A117B.4080606@multiplay.co.uk> <545B1F2A.5010203@FreeBSD.org> <20141106083153.GK53947@kib.kiev.ua> <545B4310.7000403@freebsd.org>
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On Thu, Nov 06, 2014 at 09:44:48AM +0000, Matthew Seaman wrote: > Hmmm.... well, our theory about this is that we see the effect when the > total traffic is sufficiently high that we're hitting the network > capacity, and dropping some packets. (The actual traffic load on an > individual server was big, but nothing like saturating the network. It's > the total that was maxing out our uplink to the Internet.) Gathering information according to https://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html would eliminate most doubts. So, do you use UFS ? > > We simulated the effect by sticking a test box on a 10Mb/s connection > and threw a lot of requests for a largeish (1MB) file at it. The packet > loss seems to be important -- presumably it's clogging up the available > mbufs with old packets that haven't received an ACK yet, so have to be > held onto in case they need to be resent.
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