Date: Thu, 15 Feb 2007 11:29:02 +0000 From: Chris <chrcoluk@gmail.com> To: "Steven H. Baeighkley" <stevenb@frii.com> Cc: freebsd-questions@freebsd.org Subject: Re: serious performance problems with 6.2 Release Message-ID: <3aaaa3a0702150329pcaa5e8r8da85930750ac03f@mail.gmail.com> In-Reply-To: <45D3A4D7.9000504@frii.com> References: <45D3A4D7.9000504@frii.com>
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On 15/02/07, Steven H. Baeighkley <stevenb@frii.com> wrote: > Greetings, > > We are having some bizarre performance problems on a freshly installed > 6.2 Release server. This is a supermicro superserver 6022c dual 2.0 Xeon > with 2GB RAM. These CPUs do support hyperthreading. We have done > significant testing with both hyperthreading turned on and off in the > bios and in the OS, to no avail. > > The server is configured as a web server with apache 2.2.4 php 5.2.0 and > ZendOptimizer. We are running proftpd 1.3.1rc1 and perl 5.8.8. We have > another server running 4.11 with the same exact hardware and software > versions. We have updated to the newest bios that Supermicro provides. > > The trouble is that the 6.2 box performs significantly worse than the > 4.11 server. The load on the 6.2 server is regularly between 2.0 and > 6.0. The load on the 4.11 server is between .57 and 1 despite often > servicing more connections. > > We began this process to upgrade into the 6 tree because 4 is EOL. We > kept the old 4.11 drive from this machine and when replacing it into the > box performance is excellent just like our other 4.11 box. We have tired > multiple tuning variables as recommended by both FreeBSD and apache and > tried the recommendations in the 6.2 errata as well. The 6.2 errata > states that kern.ipc.nmbclusters="0" will help the kernel memory > allocator properly deal with high network traffic. We tried this and > initially thought that the box was showing wonderful performance, but > then we realized that the box was not allowing much network access at > all. A single ssh and proftpd connection were all it would accept. > Apache wouldn't even start giving a MaxClients error. Removing this > option returned it to functional though poor performance mode. Are we > missing something with how to use this variable? IS this expected behavior? > > This particular hardware does display some oddities on both machines, > running either 6.2 or 4.11. We know that FreeBSD has hyperthreading > turned off by default. We have done some additional testing with > hyperthreading turned on in the OS, but we wish for it to remain off due > to security concerns. If we disable hyperthreading in the bios and have > it disabled in the OS then FreeBSD sees one physical and one logical > processor (from dmesg) and only uses processor 0. If we enable > hyperthreading in the bios and leave it disabled in the OS it will show > 4 CPUs but only use 0 and 2. Top will show that there is 50% idle CPU > despite the fact that the box is 100% loaded, CPU 1 and 3 are idle. We > would expect that FreeBSD would not see logical processors when > hyperthreading was disabled in either the BIOS or the OS. This may just > be a communication problem between the BIOS and FreeBSD, but we don't > see this behavior on other supermicro servers with hyperthreading. > > VMSTAT, NETSTAT, NFSSTAT and FSTAT show similar numbers between both > servers, certainly nothing that would explain why a single httpd process > requires 20% of a CPU on the 6.2 box and only 5-7% on the 4.11, but we > could easily be missing something. We suspected NFS or disk > bottlenecks, but ran IOZONE tests and found that the 6.2 box is actually > having better performance on nfs and disk access. We are running a > slightly customized SMP kernel with device polling enabled. The only > bottleneck apears to be CPU usage, which works fine on 4.11. > > From what we've read we should not be seeing these performance problems > with 6.2. So what are we missing? We assume its something stupid that > will fix this problem quickly and easily, but so far, despite all the > resources, we have been unable to find a problem with enough in common > with our own to suggest possible solutions. > > Please Help. > > thanks > Steve B > > -- > --- > Steven H. Baeighkley - Systems Administrator > Front Range Internet, Inc. > stevenb@frii.com - (970) 212-0756 > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" > I cant comment on why your cpu usage is different by so much other than freebsd 4 code is less bloated and more streamlined and I think freebsd 6 is designed in a way that efficency is lost in favour of scaling for better SMP support. kern.ipc.nmbclusters I have had problems with, I used to set to 65535 initially to help under DDOS but this reduced transfer speeds, I then tried setting to 0 as its reccomended here and is supposed to increase itself when needed but I found speeds plummeted, I was getting 20kB/sec over a lan. So now I just leave it autoset which seems the only way to get normal network performance. Chris
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