Date: Tue, 20 Nov 2007 14:56:34 +0300 From: Alexey Popov <lol@chistydom.ru> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-stable@freebsd.org Subject: Re: 2 x quad-core system is slower that 2 x dual core on FreeBSD Message-ID: <4742CB72.1060305@chistydom.ru> In-Reply-To: <fhsl0v$n85$1@ger.gmane.org> References: <4741905E.8050300@chistydom.ru> <fhs3s5$knj$1@ger.gmane.org> <47419AB3.5030008@chistydom.ru> <fhs7db$2es$1@ger.gmane.org> <4741B3DE.2000009@chistydom.ru> <fhsl0v$n85$1@ger.gmane.org>
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Hi. Ivan Voras wrote: > Some more ideas: How is your disk load (iostat, systat -vm, diskinfo -t) > during the load? You don't use NFS for the web directories, do you? > Can you run bonnie++ while the machine is idle (i.e. apache is stopped) > just to verify it isn't a stupid problem with the disks or the driver? There's almost no disk load except writing ~15 strings per second to logs. All PHP code fits in memory and there's no need to read disk. atime turned off. NFS is not used. > So, you pick the CPU out of the motherboard and plug in another one? If > not, you can't be sure that some other thing isn't wrong. I know you > tried it on Linux, but it might use slightly different commands in the > driver that don't trigger the error. I'm very surprised that both 6.x > and 7.x behave almost the same on your load: since they are very > different in how they support multiple CPU-s, I'd expect a big > difference in this case (in favour of 7.x), not a small one. This might > point that the problem is not in the OS itself, but maybe in the > hardware or in some driver. I did'nt change CPU myself, but I think this 4-core and 8-core servers (Intel SR1500 platform) are different only in CPUs. You can see it in dmesg in the root of this thread. > You don't have WITNESS, INVARIANTS, DIAGNOSTICS or something similar > enabled? Can you try a generic SMP kernel (called "SMP" in 6.x; the > "GENERIC" in 7.x has SMP by default) and see how it works? > Can you disable SMP and try with only one CPU (on the 2xquad machine)? > You can do it in loader.conf by setting kern.smp.disabled=1, or perhaps > in BIOS. If there's a problem in some hardware or a driver, you'd still > get a big load on sys time. You might also want to halt certain logical > CPUs in the OS itself (see smp(4) man page) and see if there's a certain > relationship between how many CPUs are running and what the sys load is. Thank you. I need some time to try all this. I'll report if find something. With best regards, Alexey Popov
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