At 07:35 PM 10/14/2002, you wrote: >I'm new to the CPU-level stuff and don't have much background in them. So >some of the terms are new for me. Let me get really basic: why would you >want multiple processors on a motherboard as opposed to a single fast >processor? More is always better, unless you start talking about a drowning man and cups of water. As for wanting multiple processors instead of a single fast one, you of course would always want to have the fastest processor(s) in the greatest numbers. In some multi-user environments jobs are numerous, but small and are often run by many users simultaneously. In this case, a multi-processor machine would be preferable over a single processor machine since the jobs can be run at the same time without being queued. Jobs that take more time will benefit from a faster processor. What you want to keep in mind when looking at a multi-processor machine is the type of application(s) you plan on running. If the application is not multi-threaded, you will not benefit from the extra processor(s) unless you are running multiple jobs simultaneously. >I take it that the Xeon line is for multiple CPU motherboards -- you don't >just run one Xeon, am I right? What does it mean, to be 'cpu cache bound'? Yes, Xeon's were designed for MP. From what I understand, you can run a single Xeon, which in effect is a just a P4. You can of course read more and have a visual comparison at: http://intel.com/support/processors/xeon/diff.htm and http://intel.com/support/processors/pentium4/p4compare.htm or google it. As for being cache-bound, (my layman's understanding) just think of the cache as being a super-fast storage area. Instead of having to pull the data across the FSB, the data is stored on the CPU-die making access time as close to real time as you can get. More info at: http://www-2.cs.cmu.edu/~tcm/thesis/subsubsection2_10_1_3_2.html >Do your comments also mean the Red Hat kernel won't need testing on the >new Hyper Threaded P4s? I have a couple of dual 2Ghz Xeons each with 2GB of PC800, one running hyperthreaded, one running normal. Depending on the job, the overhead associated with running hyperthreaded is enormous. Here are some stats for you: [cph@blur ~]$ cat /proc/version /proc/cpuinfo /proc/meminfo Linux version 2.4.9-34smp (bhcompile@daffy.perf.redhat.com) (gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-108.1)) #1 SMP Sat Jun 1 06:15:25 EDT 2002 processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) XEON(TM) CPU 2.00GHz stepping : 4 cpu MHz : 1995.162 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 3984.58 processor : 1 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) XEON(TM) CPU 2.00GHz stepping : 4 cpu MHz : 1995.162 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 3984.58 total: used: free: shared: buffers: cached: Mem: 2107416576 2077827072 29589504 0 458694656 1494269952 Swap: 1077501952 0 1077501952 MemTotal: 2058024 kB MemFree: 28896 kB MemShared: 0 kB Buffers: 447944 kB Cached: 1459248 kB SwapCached: 0 kB Active: 1211376 kB Inact_dirty: 454344 kB Inact_clean: 241472 kB Inact_target: 524016 kB HighTotal: 1178560 kB HighFree: 15324 kB LowTotal: 879464 kB LowFree: 13572 kB SwapTotal: 1052248 kB SwapFree: 1052248 kB and the machine with hyperthreading enabled shows: [cph@conroe ~]$ cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) XEON(TM) CPU 2.00GHz stepping : 4 cpu MHz : 1995.164 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 3984.58 processor : 1 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) XEON(TM) CPU 2.00GHz stepping : 4 cpu MHz : 1995.164 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 3984.58 processor : 2 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) XEON(TM) CPU 2.00GHz stepping : 4 cpu MHz : 1995.164 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 3984.58 processor : 3 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) XEON(TM) CPU 2.00GHz stepping : 4 cpu MHz : 1995.164 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 3984.58 [cph@conroe ~]$ cat /proc/meminfo total: used: free: shared: buffers: cached: Mem: 2113667072 2008354816 105312256 0 212000768 1683333120 Swap: 2146754560 0 2146754560 MemTotal: 2064128 kB MemFree: 102844 kB MemShared: 0 kB Buffers: 207032 kB Cached: 1643880 kB SwapCached: 0 kB Active: 948732 kB Inact_dirty: 848948 kB Inact_clean: 62824 kB Inact_target: 372100 kB HighTotal: 1178560 kB HighFree: 19404 kB LowTotal: 885568 kB LowFree: 83440 kB SwapTotal: 2096440 kB SwapFree: 2096440 kB Committed_AS: 7888 kB As a speed test, I ran some test certifications of our statistical software, the machine running in hyperthreaded mode was significantly slower than the dual Xeon running in "native" mode. We have a certification script that I put in a batch, kicking off two on the dual Xeon and four on the dual Xeon running hyperthreaded. non-hyper: real 33m38.261s user 31m38.750s sys 1m48.790s real 33m40.230s user 31m40.630s sys 1m48.660s hyperthread enabled: real 58m31.635s user 56m5.110s sys 2m5.660s real 58m43.463s user 56m10.390s sys 2m8.450s real 58m56.267s user 56m20.470s sys 2m10.940s real 58m59.632s user 56m27.340s sys 2m6.860s So, while it could be argued that the hyperthreaded machine suffered a bit from being I/O bound on the harddrive, that period of time was negligible versus being cache-bound as stated by Mr. Flory below. Also to note there is some overhead which I have not investigated on how the kernel handles hyperthreading. A top shows: PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND 1 root 15 0 404 404 356 S 0.0 0.0 0:10 init 2 root 0K 0 0 0 0 SW 0.0 0.0 0:00 migration_CPU0 3 root 0K 0 0 0 0 SW 0.0 0.0 0:00 migration_CPU1 4 root 0K 0 0 0 0 SW 0.0 0.0 0:00 migration_CPU2 5 root 0K 0 0 0 0 SW 0.0 0.0 0:00 migration_CPU3 6 root 15 0 0 0 0 SW 0.0 0.0 0:00 keventd 7 root 34 19 0 0 0 SWN 0.0 0.0 0:02 ksoftirqd_CPU0 8 root 34 19 0 0 0 SWN 0.0 0.0 0:00 ksoftirqd_CPU1 9 root 34 19 0 0 0 SWN 0.0 0.0 0:00 ksoftirqd_CPU2 10 root 34 19 0 0 0 SWN 0.0 0.0 0:00 ksoftirqd_CPU3 Where "migration_CPUX" is not seen on the non-hyperthreaded version. What is interesting to notice is that the migration process never consumes time, memory or CPU. hmmmmmmmm. Pete >Thanks > >Bob Cochran > >Samuel Flory wrote: > >>Red Hat has support this since one of the 7.2 kernel updates. This is old >>hat on the current crop of Xeon (aka P4 Xeon). Linux treats them as >>multiple cpus. Don't assume that this will make your system faster. If >>you tend to only one process active at a time then it will slow things >>down. It's also really bad if you are cpu cache bound. >> >> >> > > > >-- >Psyche-list mailing list >Psyche-list@redhat.com >https://listman.redhat.com/mailman/listinfo/psyche-list -------------------------- Pete Huckelba Stata Corporation 4905 Lakeway Drive College Station, TX 77845 (979)696-4600 -- Psyche-list mailing list Psyche-list@redhat.com https://listman.redhat.com/mailman/listinfo/psyche-list
