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 ([EMAIL PROTECTED]) (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
ThanksBob 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 [EMAIL PROTECTED] https://listman.redhat.com/mailman/listinfo/psyche-list
-------------------------- Pete Huckelba Stata Corporation 4905 Lakeway Drive College Station, TX 77845 (979)696-4600
