* Counting CPU_CLK_UNHALTED on an idle system
@ 2007-07-13 12:33 John Sigler
2007-07-13 12:37 ` Stephane Eranian
0 siblings, 1 reply; 4+ messages in thread
From: John Sigler @ 2007-07-13 12:33 UTC (permalink / raw)
To: linux-rt-users, oprofile-list
[ Note: cross-posted to linux-rt-users and oprofile-list ]
Hello,
The x86 Performance Monitoring Event "CPU_CLK_UNHALTED" is defined as:
Number of cycles during which the processor is not halted.
IIUC, when the CPU is in the HALT state, CPU_CLK_UNHALTED should not
increment, right? When Linux has nothing to do, it executes HLT.
http://lxr.linux.no/source/arch/i386/kernel/process.c#L101
I set up OProfile to sample EIP every 200000 CPU_CLK_UNHALTED cycles on
an idle system. I was expecting a very small number of samples, since
CPU_CLK_UNHALTED should not increment (most of the time).
I ran the daemon 5 minutes on a idle system
# opreport -l
CPU: PIII, speed 1266.7 MHz (estimated)
Counted CPU_CLK_UNHALTED events (clocks processor is not halted) with a
unit mask of 0x00 (No unit mask) count 200000
samples % symbol name
1868484 99.4914 cpu_idle
4560 0.2428 (oprofiled)
727 0.0387 ip_route_input
457 0.0243 acpi_ev_asynch_execute_gpe_method
454 0.0242 ip_route_output_slow
286 0.0152 dma_free_coherent
280 0.0149 ip_route_input_slow
273 0.0145 acpi_ex_opcode_6A_0T_1R
220 0.0117 __acpi_nmi_disable
130 0.0069 Dta1xxRxProcessStatusFlags
94 0.0050 Dta1xxTxProcessStatusFlags
93 0.0050 (bash)
85 0.0045 Dta1xxIsr
79 0.0042 intel_machine_check
56 0.0030 sys_olduname
51 0.0027 Dta1xxPeriodicIntHandler
cpu_idle breakdown:
c0100e70 1 5.4e-05
c0100e71 1 5.4e-05
c0100e78 1 5.4e-05
c0100e88 1 5.4e-05
c0100e8a 1 5.4e-05
c0100e97 4 2.1e-04
c0100ea8 1868475 99.9995
cpu_idle objdump:
c0100ea6: fb sti
c0100ea7: f4 hlt
c0100ea8: eb 0b jmp c0100eb5
(If an interrupt is used to resume execution after a HLT instruction,
the saved instruction pointer points to the instruction following the
HLT instruction.)
oprofiled collected 1878300 samples. In other words, the system received
1878300 NMIs. (5 * 60 * 1.2667e9) / 1878300 = 202316 cycles between NMI
Seems like CPU_CLK_UNHALTED increments every cycle.
Perhaps HLT does not put my CPU in the HALT state?
Did I miss something?
Regards.
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: Counting CPU_CLK_UNHALTED on an idle system
2007-07-13 12:33 Counting CPU_CLK_UNHALTED on an idle system John Sigler
@ 2007-07-13 12:37 ` Stephane Eranian
2007-07-13 13:02 ` John Sigler
0 siblings, 1 reply; 4+ messages in thread
From: Stephane Eranian @ 2007-07-13 12:37 UTC (permalink / raw)
To: John Sigler; +Cc: linux-rt-users, oprofile-list
John,
On PIII, CPU_CLK_UNHALTED is broken and keeps on counting while in HALT state.
On Fri, Jul 13, 2007 at 02:33:09PM +0200, John Sigler wrote:
> [ Note: cross-posted to linux-rt-users and oprofile-list ]
>
> Hello,
>
> The x86 Performance Monitoring Event "CPU_CLK_UNHALTED" is defined as:
> Number of cycles during which the processor is not halted.
>
> IIUC, when the CPU is in the HALT state, CPU_CLK_UNHALTED should not
> increment, right? When Linux has nothing to do, it executes HLT.
>
> http://lxr.linux.no/source/arch/i386/kernel/process.c#L101
>
> I set up OProfile to sample EIP every 200000 CPU_CLK_UNHALTED cycles on
> an idle system. I was expecting a very small number of samples, since
> CPU_CLK_UNHALTED should not increment (most of the time).
>
> I ran the daemon 5 minutes on a idle system
>
> # opreport -l
> CPU: PIII, speed 1266.7 MHz (estimated)
> Counted CPU_CLK_UNHALTED events (clocks processor is not halted) with a
> unit mask of 0x00 (No unit mask) count 200000
> samples % symbol name
> 1868484 99.4914 cpu_idle
> 4560 0.2428 (oprofiled)
> 727 0.0387 ip_route_input
> 457 0.0243 acpi_ev_asynch_execute_gpe_method
> 454 0.0242 ip_route_output_slow
> 286 0.0152 dma_free_coherent
> 280 0.0149 ip_route_input_slow
> 273 0.0145 acpi_ex_opcode_6A_0T_1R
> 220 0.0117 __acpi_nmi_disable
> 130 0.0069 Dta1xxRxProcessStatusFlags
> 94 0.0050 Dta1xxTxProcessStatusFlags
> 93 0.0050 (bash)
> 85 0.0045 Dta1xxIsr
> 79 0.0042 intel_machine_check
> 56 0.0030 sys_olduname
> 51 0.0027 Dta1xxPeriodicIntHandler
>
> cpu_idle breakdown:
>
> c0100e70 1 5.4e-05
> c0100e71 1 5.4e-05
> c0100e78 1 5.4e-05
> c0100e88 1 5.4e-05
> c0100e8a 1 5.4e-05
> c0100e97 4 2.1e-04
> c0100ea8 1868475 99.9995
>
> cpu_idle objdump:
>
> c0100ea6: fb sti
> c0100ea7: f4 hlt
> c0100ea8: eb 0b jmp c0100eb5
>
> (If an interrupt is used to resume execution after a HLT instruction,
> the saved instruction pointer points to the instruction following the
> HLT instruction.)
>
> oprofiled collected 1878300 samples. In other words, the system received
> 1878300 NMIs. (5 * 60 * 1.2667e9) / 1878300 = 202316 cycles between NMI
>
> Seems like CPU_CLK_UNHALTED increments every cycle.
>
> Perhaps HLT does not put my CPU in the HALT state?
>
> Did I miss something?
>
> Regards.
>
>
> -------------------------------------------------------------------------
> This SF.net email is sponsored by DB2 Express
> Download DB2 Express C - the FREE version of DB2 express and take
> control of your XML. No limits. Just data. Click to get it now.
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> _______________________________________________
> oprofile-list mailing list
> oprofile-list@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/oprofile-list
--
-Stephane
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Counting CPU_CLK_UNHALTED on an idle system
2007-07-13 12:37 ` Stephane Eranian
@ 2007-07-13 13:02 ` John Sigler
2007-07-13 13:09 ` Stephane Eranian
0 siblings, 1 reply; 4+ messages in thread
From: John Sigler @ 2007-07-13 13:02 UTC (permalink / raw)
To: eranian; +Cc: linux-rt-users, oprofile-list
Stephane Eranian wrote:
> On PIII, CPU_CLK_UNHALTED is broken and keeps on counting while in HALT state.
Stephane,
Would you have a reference?
There is no such mention in the latest Specification Update (May 2007).
http://developer.intel.com/design/intarch/specupdt/244453.htm
Regards.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Counting CPU_CLK_UNHALTED on an idle system
2007-07-13 13:02 ` John Sigler
@ 2007-07-13 13:09 ` Stephane Eranian
0 siblings, 0 replies; 4+ messages in thread
From: Stephane Eranian @ 2007-07-13 13:09 UTC (permalink / raw)
To: John Sigler; +Cc: linux-rt-users, oprofile-list
John,
On Fri, Jul 13, 2007 at 03:02:12PM +0200, John Sigler wrote:
> Stephane Eranian wrote:
>
> > On PIII, CPU_CLK_UNHALTED is broken and keeps on counting while in HALT state.
>
> Stephane,
>
> Would you have a reference?
>
No references, just my presonal experience. You'd have to ask Intel for a confirmation
or just file a bug report. I don't know where, unfortunately.
Note that the event works on Pentium M.
> There is no such mention in the latest Specification Update (May 2007).
>
> http://developer.intel.com/design/intarch/specupdt/244453.htm
>
> Regards.
>
> -------------------------------------------------------------------------
> This SF.net email is sponsored by DB2 Express
> Download DB2 Express C - the FREE version of DB2 express and take
> control of your XML. No limits. Just data. Click to get it now.
> http://sourceforge.net/powerbar/db2/
> _______________________________________________
> oprofile-list mailing list
> oprofile-list@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/oprofile-list
--
-Stephane
^ permalink raw reply [flat|nested] 4+ messages in thread
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2007-07-13 12:33 Counting CPU_CLK_UNHALTED on an idle system John Sigler
2007-07-13 12:37 ` Stephane Eranian
2007-07-13 13:02 ` John Sigler
2007-07-13 13:09 ` Stephane Eranian
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