Messages in this thread | | | Date | Thu, 16 May 2002 00:41:36 -0700 | From | Andrew Morton <> | Subject | Re: [RFC][PATCH] iowait statistics |
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Denis Vlasenko wrote: > > On 14 May 2002 00:18, Andrew Morton wrote: > > Rik van Riel wrote: > > > 4) on SMP systems the iowait time can be overestimated, no big > > > deal IMHO but cheap suggestions for improvement are welcome > > > > I suspect that a number of these statistical accounting mechanisms > > are going to break. The new irq-affinity code works awfully well. > > > > The kernel profiler in 2.5 doesn't work very well at present. > > When investigating this, I ran a busy-wait process. It attached > > itself to CPU #3 and that CPU received precisely zero interrupts > > across a five minute period. So the profiler cunningly avoids profiling > > busy CPUs, which is rather counter-productive. Fortunate that oprofile > > uses NMI. > > What, even local APIC interrupts did not happen on CPU#3 > in these five mins?
CPU1 is busy:
quad:/home/akpm> cat /proc/interrupts ; sleep 10 ; cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 0: 36059 33847 38948 33846 IO-APIC-edge timer 1: 1 1 1 4 IO-APIC-edge keyboard 2: 0 0 0 0 XT-PIC cascade 4: 1 1 1 0 IO-APIC-edge GDB-stub 8: 0 0 0 1 IO-APIC-edge rtc 12: 0 1 0 0 IO-APIC-edge PS/2 Mouse 14: 1 2 0 3 IO-APIC-edge ide0 15: 7558 7557 7633 8025 IO-APIC-edge ide1 19: 17088 17707 17210 18610 IO-APIC-level ide2, ide3, ide4, ide5 35: 38 71 56 174 IO-APIC-level aic7xxx 38: 955 1798 584 517 IO-APIC-level eth0 58: 25368 19911 27931 20695 IO-APIC-level aic7xxx NMI: 164030 164030 164030 164030 LOC: 142543 142543 142542 142542 ERR: 0 MIS: 0 CPU0 CPU1 CPU2 CPU3 0: 36388 33847 39289 34178 IO-APIC-edge timer 1: 1 1 1 4 IO-APIC-edge keyboard 2: 0 0 0 0 XT-PIC cascade 4: 1 1 1 0 IO-APIC-edge GDB-stub 8: 0 0 0 1 IO-APIC-edge rtc 12: 0 1 0 0 IO-APIC-edge PS/2 Mouse 14: 1 2 0 3 IO-APIC-edge ide0 15: 7565 7557 7633 8026 IO-APIC-edge ide1 19: 17088 17707 17210 18610 IO-APIC-level ide2, ide3, ide4, ide5 35: 38 71 56 174 IO-APIC-level aic7xxx 38: 969 1798 590 525 IO-APIC-level eth0 58: 25368 19911 27931 20695 IO-APIC-level aic7xxx NMI: 165032 165032 165032 165032 LOC: 143545 143545 143544 143544 ERR: 0 MIS: 0
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