Date: Sun, 27 Nov 2011 04:17:07 +1100 From: Lawrence Stewart <lstewart@freebsd.org> To: George Mitchell <george+freebsd@m5p.com> Cc: freebsd-stable@freebsd.org Subject: Re: TCP Reassembly Issues Message-ID: <4ED11F13.8090501@freebsd.org> In-Reply-To: <4ED110FA.4060406@m5p.com> References: <CAPNZ-Wq38=F3o2hYuYF_unBj3SZQ52XhVhdcwQ8PE_vU9xc2YA@mail.gmail.com> <4ECEF6FD.5050006@freebsd.org> <4ED077BF.10205@freebsd.org> <4ED110FA.4060406@m5p.com>
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Hi George, On 11/27/11 03:16, George Mitchell wrote: > On 11/26/11 00:23, Lawrence Stewart wrote: >> [...] >> Could those who have reported the bug and are able to recompile their >> kernel to test a patch please try the following and report back to the >> list: >> >> http://people.freebsd.org/~lstewart/patches/misctcp/tcp_reass_plugzoneleak_10.x.r227986.patch >> >> [...] > Works for me! I'm now getting a sustained throughput of 7.4MB/s, > compared to 4.3MB/s on 8.2-STABLE and 3.2MB/s on 7.4-RELEASE, all on > the same hardware (HP notebook with re 100Mb/s interface, reading from > an 8.2-STABLE server with an alc 1000Mb/s interface, via two gigabit > switches). Good stuff. > But I'm still bemused that there should have been any TCP reassembly > going on. Doesn't that imply that there was packet fragmentation? My > network is uniformly 1500 byte MTU. -- George TCP reassembly refers to queuing packets received out of order until the missing segment is received i.e. not IP layer fragmentation related, but packet loss or packet reordering related. I guess something in your setup is dropping the odd packet which is why your NFS performance isn't closer to the 10+MB/s (I'm not sure how much overhead NFS adds, but ~12MB/s is max application-layer throughput of 100Mbps Ethernet so achievable NFS throughput should be a bit less than that) it could be if everything was peachy. siftr(4) and some tcpdumping on both client/server could probably help you figure out where you're dropping packets if you want to improve your current performance even further. Cheers, Lawrence
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