Re: sched /HT processor

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I looked at my "include/asm-i386/param.h" and the HZ value is 1000.So, I suppose the timer interrupt frequency is 1000 times per sec. or once every 1 millisec.
So, is scheduler_tick() ( for resceduling) called only once every 1 ms?? I am measuring the time when 2 of my processes are scheduled in a HT processor.So, the possible timedifference of when my 2 processes are scheduled can be only the following: 

1) 0 (if both of my processes are scheduled @ the same time since its a HT)
2) 1ms ( this is the min. possible time diff.
3) some value greater than 1 ms
Is the above argument correct?

Thanks


From: Steven Rostedt <[email protected]>
To: Arun Srinivas <[email protected]>
CC: LKML <[email protected]>
Subject: Re: sched /HT processor
Date: Sat, 02 Apr 2005 20:17:54 -0500

On Sun, 2005-04-03 at 06:07 +0530, Arun Srinivas wrote:
> HI
>
> I have pentium4 hyperthreaded processor.I am using kernel 2.6.5 and i
> rebuilt my kernel with CONFIG_SMP enabled (in this kernel source there is 
> nothing such as CONFIG_SMT...i noticed this only in recent 2.6.11).
>

I don't have a 2.6.5 available, but I do have a 2.6.9 to look at.
> 1) So, after I rebulit it with CONFIG_SMP enabled does linux recogonize my > machine as hyperthreaded or as 2 seperate processor? Also, if it does not 
> recogonize it as hyperthreaded(but only as 2 seperate CPU's), does the
> scheduler schedule instruction in the 2 cpu's independently? (does it
> maintain 2 seperate runqueues?
>

I believe even HT on 2.6.11 maintains two different runqueues.  But it
doesn't care so much to jump from one runqueue to the next if it is HT.
> 2) If it has indeed recogonized this as hyperthreaded processor...does the 
> scheduler use a common runqueue for the 2 logical processor?
>

No, you wouldn't want to.


> (please read below)

What do you want us to see?
> ********************************************************************************************************* 
> (I am attaching the ouput of  'dmesg' (command)  on my machine)
> ************************************************************************************************************* 
> Apr  2 17:43:12 kulick2 kernel: Linux version 2.6.5-1.358custom
> (root@kulick2) (gcc version 3.3
> .3 20040412 (Red Hat Linux 3.3.3-7)) #133 SMP Wed Mar 30 12:16:27 CST 2005 
> Apr  2 17:43:12 kulick2 kernel: BIOS-provided physical RAM map:
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 0000000000000000 -
> 00000000000a0000 (usable)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 00000000000f0000 -
> 0000000000100000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 0000000000100000 -
> 000000001f770000 (usable)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 000000001f770000 -
> 000000001f772000 (ACPI NVS)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 000000001f772000 -
> 000000001f793000 (ACPI data)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 000000001f793000 -
> 000000001f800000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 00000000fec00000 -
> 00000000fec10000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 00000000fecf0000 -
> 00000000fecf1000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 00000000fed20000 -
> 00000000fed90000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 00000000fee00000 -
> 00000000fee10000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 00000000ffb00000 -
> 0000000100000000 (reserved)
> Apr  2 17:43:12 kulick2 kernel: 0MB HIGHMEM available.
> Apr  2 17:43:12 kulick2 kernel: 503MB LOWMEM available.
> Apr 2 17:43:12 kulick2 kernel: ACPI: S3 and PAE do not like each other for 
> now, S3 disabled.
> Apr  2 17:43:12 kulick2 kernel: found SMP MP-table at 000fe710
> Apr  2 17:43:12 kulick2 kernel: On node 0 totalpages: 128880
> Apr  2 17:43:12 kulick2 kernel:   DMA zone: 4096 pages, LIFO batch:1
> Apr 2 17:43:12 kulick2 kernel: Normal zone: 124784 pages, LIFO batch:16 
> Apr  2 17:43:12 kulick2 kernel:   HighMem zone: 0 pages, LIFO batch:1
> Apr  2 17:43:12 kulick2 kernel: DMI 2.3 present.
> Apr  2 17:43:12 kulick2 kernel: Using APIC driver default
> Apr  2 17:43:12 kulick2 kernel: ACPI: RSDP (v000 DELL
>                ) @
> 0x000feba0
> Apr 2 17:43:12 kulick2 kernel: ACPI: RSDT (v001 DELL GX270 0x00000007 
> ASL  0x00000061) @
> 0x000fd192
> Apr 2 17:43:12 kulick2 kernel: ACPI: FADT (v001 DELL GX270 0x00000007 
> ASL  0x00000061) @
> 0x000fd1ca
> Apr 2 17:43:12 kulick2 kernel: ACPI: SSDT (v001 DELL st_ex 0x00001000 
> MSFT 0x0100000d) @
> 0xfffd4eee
> Apr  2 17:43:12 kulick2 irqbalance: irqbalance startup succeeded
> Apr 2 17:43:12 kulick2 kernel: ACPI: MADT (v001 DELL GX270 0x00000007 
> ASL  0x00000061) @
> 0x000fd23e
> Apr 2 17:43:12 kulick2 kernel: ACPI: BOOT (v001 DELL GX270 0x00000007 
> ASL  0x00000061) @
> 0x000fd2aa
> Apr 2 17:43:12 kulick2 kernel: ACPI: ASF! (v016 DELL GX270 0x00000007 
> ASL  0x00000061) @
> 0x000fd2d2
> Apr 2 17:43:12 kulick2 kernel: ACPI: DSDT (v001 DELL dt_ex 0x00001000 
> MSFT 0x0100000d) @
> 0x00000000
> Apr  2 17:43:12 kulick2 kernel: ACPI: PM-Timer IO Port: 0x808
> Apr 2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] 
> enabled)
> Apr  2 17:43:12 kulick2 kernel: Processor #0 15:2 APIC version 20
> Apr 2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] 
> enabled)
> Apr  2 17:43:12 kulick2 kernel: Processor #1 15:2 APIC version 20
> Apr 2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x03] lapic_id[0x01] 
> disabled)
> Apr 2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x04] lapic_id[0x03] 
> disabled)
> Apr 2 17:43:12 kulick2 kernel: ACPI: IOAPIC (id[0x02] address[0xfec00000] 
> global_irq_base[0x0]
> )
> Apr  2 17:43:12 kulick2 kernel: IOAPIC[0]: Assigned apic_id 2
> Apr 2 17:43:12 kulick2 kernel: IOAPIC[0]: apic_id 2, version 32, address 
> 0xfec00000, GSI 0-23
> Apr  2 17:43:12 kulick2 kernel: ACPI: INT_SRC_OVR (bus 0 bus_irq 0
> global_irq 2 dfl dfl)
> Apr  2 17:43:12 kulick2 kernel: ACPI: INT_SRC_OVR (bus 0 bus_irq 9
> global_irq 9 high level)
> Apr  2 17:43:12 kulick2 kernel: Enabling APIC mode:  Flat.  Using 1 I/O
> APICs
> Apr  2 17:43:12 kulick2 kernel: Using ACPI (MADT) for SMP configuration
> information
> Apr  2 17:43:12 kulick2 portmap: portmap startup succeeded
> Apr  2 17:43:12 kulick2 kernel: Built 1 zonelists
> Apr 2 17:43:12 kulick2 kernel: Kernel command line: ro root=LABEL=/ rhgb 
> quiet
> Apr  2 17:43:12 kulick2 kernel: mapped 4G/4G trampoline to fffeb000.
> Apr  2 17:43:12 kulick2 kernel: Initializing CPU#0
> Apr 2 17:43:12 kulick2 kernel: CPU 0 irqstacks, hard=023cb000 soft=023ab000 
> Apr  2 17:43:12 kulick2 kernel: PID hash table entries: 2048 (order 11:
> 16384 bytes)
> Apr  2 17:43:12 kulick2 kernel: Detected 2993.225 MHz processor.
> Apr  2 17:43:12 kulick2 kernel: Using pmtmr for high-res timesource
> Apr  2 17:43:12 kulick2 kernel: Console: colour VGA+ 80x25
> Apr  2 17:43:12 kulick2 kernel: Memory: 505996k/515520k available (1744k
> kernel code, 8772k res
> erved, 756k data, 180k init, 0k highmem)
> Apr 2 17:43:12 kulick2 kernel: Calibrating delay loop... 5931.00 BogoMIPS 
> Apr  2 17:43:12 kulick2 kernel: Security Scaffold v1.0.0 initialized
> Apr  2 17:43:12 kulick2 kernel: SELinux:  Initializing.
> Apr  2 17:43:12 kulick2 kernel: SELinux:  Starting in permissive mode
> Apr  2 17:43:12 kulick2 kernel: There is already a security framework
> initialized, register_sec
> urity failed.
> Apr 2 17:43:12 kulick2 kernel: Failure registering capabilities with the 
> kernel
> Apr  2 17:43:12 kulick2 kernel: selinux_register_security:  Registering
> secondary module capabi
> lity
> Apr  2 17:43:12 kulick2 kernel: Capability LSM initialized
> Apr  2 17:43:12 kulick2 kernel: Dentry cache hash table entries: 32768
> (order: 5, 131072 bytes)
> Apr  2 17:43:12 kulick2 kernel: Inode-cache hash table entries: 32768
> (order: 5, 131072 bytes)
> Apr 2 17:43:12 kulick2 kernel: Mount-cache hash table entries: 512 (order: 
> 0, 4096 bytes)
> Apr 2 17:43:12 kulick2 kernel: CPU: Trace cache: 12K uops, L1 D cache: 8K 
> Apr  2 17:43:12 kulick2 rpc.statd[2019]: Version 1.0.6 Starting
> Apr  2 17:43:12 kulick2 kernel: CPU: L2 cache: 512K
> Apr  2 17:43:12 kulick2 kernel: CPU: Physical Processor ID: 0
> Apr  2 17:43:12 kulick2 rpc.statd[2019]: gethostbyname error for kulick2
> Apr 2 17:43:12 kulick2 kernel: Intel machine check architecture supported. 
> Apr  2 17:43:12 kulick2 kernel: Intel machine check reporting enabled on
> CPU#0.
> Apr  2 17:43:12 kulick2 nfslock: rpc.statd startup succeeded
> Apr 2 17:43:12 kulick2 kernel: CPU#0: Intel P4/Xeon Extended MCE MSRs (12) 
> available
> Apr  2 17:43:12 kulick2 kernel: CPU#0: Thermal monitoring enabled
> Apr 2 17:43:12 kulick2 kernel: Enabling fast FPU save and restore... done. 
> Apr  2 17:43:12 kulick2 kernel: Enabling unmasked SIMD FPU exception
> support... done.
> Apr  2 17:43:12 kulick2 kernel: Checking 'hlt' instruction... OK.
> Apr  2 17:43:12 kulick2 kernel: POSIX conformance testing by UNIFIX
> Apr  2 17:43:12 kulick2 kernel: CPU0: Intel(R) Pentium(R) 4 CPU 3.00GHz
> stepping 09
> Apr  2 17:43:12 kulick2 kernel: per-CPU timeslice cutoff: 1462.93 usecs.
> Apr 2 17:43:12 kulick2 kernel: task migration cache decay timeout: 2 msecs. 
> Apr  2 17:43:12 kulick2 kernel: enabled ExtINT on CPU#0
> Apr 2 17:43:12 kulick2 kernel: ESR value before enabling vector: 00000040 > Apr 2 17:43:12 kulick2 kernel: ESR value after enabling vector: 00000000 
> Apr  2 17:43:12 kulick2 kernel: Booting processor 1/1 eip 2000
> Apr 2 17:43:12 kulick2 kernel: CPU 1 irqstacks, hard=023cc000 soft=023ac000 
> Apr  2 17:43:12 kulick2 kernel: Initializing CPU#1
> Apr  2 17:43:12 kulick2 kernel: masked ExtINT on CPU#1
> Apr 2 17:43:12 kulick2 kernel: ESR value before enabling vector: 00000000 > Apr 2 17:43:12 kulick2 kernel: ESR value after enabling vector: 00000000 > Apr 2 17:43:12 kulick2 kernel: Calibrating delay loop... 5980.16 BogoMIPS > Apr 2 17:43:12 kulick2 kernel: CPU: Trace cache: 12K uops, L1 D cache: 8K 
> Apr  2 17:43:12 kulick2 kernel: CPU: L2 cache: 512K
> Apr  2 17:43:12 kulick2 kernel: CPU: Physical Processor ID: 0
> Apr 2 17:43:12 kulick2 kernel: Intel machine check architecture supported. 
> Apr  2 17:43:12 kulick2 kernel: Intel machine check reporting enabled on
> CPU#1.
> Apr 2 17:43:12 kulick2 kernel: CPU#1: Intel P4/Xeon Extended MCE MSRs (12) 
> available
> Apr  2 17:43:12 kulick2 kernel: CPU#1: Thermal monitoring enabled
> Apr  2 17:43:12 kulick2 kernel: CPU1: Intel(R) Pentium(R) 4 CPU 3.00GHz
> stepping 09
> Apr 2 17:43:12 kulick2 kernel: Total of 2 processors activated (11911.16 
> BogoMIPS).
> Apr  2 17:43:12 kulick2 kernel: cpu_sibling_map[0] = 1
> Apr  2 17:43:12 kulick2 kernel: cpu_sibling_map[1] = 0

Here you see that you have two CPUs.  0 is the sibling of 1 and 1 to 0.
This just shows that you have HT.  If you were to have a dual xeon, then
you would see 4 CPUs and two pairs.

-- Steve



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