Messages in this thread | | | Date | Thu, 23 Aug 2007 15:05:14 -0400 | From | "Jeff Bloom" <> | Subject | kernel version 2.6.11-12 : Apic fires less often on Intel quad Cores x5355 than on other platforms |
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Problem: The local apic interrupt fires less often on a Quad core x5355 Intel Xeon CPU 2.67GHz than on an Intel 3.2GHz Xeon system running the same kernel version 2.6.11.12
Description: Specifically the local apic fires 984 times a second on the Quad core and 1000 times on the 3.2GHz Xeon. The expected result is to have both platforms receive the apic interrupt 1000 times a second.
Question: Are there any isolated apic patches which may account for this behaviour? Some obscure errata for this apic configured with a different divisor?
I certainly see some rework in 2.6.22 kernels apic.c but I'm not sure it addresses this issue specifically.
Has anyone else encountered this issue?
Detailed info below: (dmesg kernel command line with apic=verbose)
3.2GHz: calibrating APIC timer ... ..... CPU clock speed is 3191.0619 MHz. ..... host bus clock speed is 199.0476 MHz.
2.67GHz Quad Core: calibrating APIC timer ... ..... CPU clock speed is 2659.0967 MHz. ..... host bus clock speed is 332.0495 MHz.
Validation of what I'm seeing below: test 1: running /proc/stat; sleep 1; /proc/stat 3.2GHz: cpu 607 5 487 5620413 1974 25 89 0 <- 1st reading cpu 607 5 487 5620815 1974 26 89 0 <- 2nd reading delta 402/(4 cpus) = 100.5 <- Adding up deltas (mostly from idle time) 2.67Ghz: (Quad core) cpu 391 1 354 12566716 1028 24 42 0 cpu 391 1 354 12567503 1028 24 42 0 delta 787/(8 cpus) = 98.38
I also see the same result looking at LOC in the /proc/interrupts which confirm 984 interrupts instead of the expected 1000.
cat /proc/interrupts |grep LOC; sleep 1; cat /proc/interrupts |grep LOC <inserting cpu labels> CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7 LOC: 15900999 15901079 15900473 15901014 15901027 15901077 15901022 15901022
LOC: 15901983 15902063 15901457 15901998 15902011 15902061 15902006 15902006
Following CPU0(15901983-15900999) = 984 The deltas show the apic interrupt interval must not be setup properly on the Quad Xeon core.
Thanks for any information you can provide. If you need more information: lspci, full dmesg, etc please let me know. - Jeff Bloom - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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