Date: Wed, 21 Aug 2013 19:12:38 +0200 From: Andre Oppermann <andre@freebsd.org> To: Julian Elischer <julian@freebsd.org> Cc: FreeBSD Net <net@FreeBSD.org> Subject: Re: TSO and FreeBSD vs Linux Message-ID: <5214F506.3070706@freebsd.org> In-Reply-To: <520A6D07.5080106@freebsd.org> References: <520A6D07.5080106@freebsd.org>
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On 13.08.2013 19:29, Julian Elischer wrote: > I have been tracking down a performance embarrassment on AMAZON EC2 and have found it I think. > Our OS cousins over at Linux land have implemented some interesting behaviour when TSO is in use. There used to be a different problem with EC2 and FreeBSD TSO. The Xen hypervisor doesn't like large 64K TSO bursts we generate, the drivers drops the whole TSO chain, TCP gets upset and turns off TSO alltogether leaving the connection going at one packet a time as in the old days. The problem is already fixed in recent EC2 9-stable images provided by cperciva. -- Andre
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