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Merged vs. User-Only - Inclusive Time

Merged vs. User-Only - Inclusive Time. Merged vs. User-Only - Exclusive Time. 1. Observing Program-OS Interaction Example 1: "Interrupts” (Interrupts induced by large number of icmp pings). NAS Parallel Benchmark SP Class W run with and without interrupts. User-Only Inclusive Time View.

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Merged vs. User-Only - Inclusive Time

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  1. Merged vs. User-Only - Inclusive Time

  2. Merged vs. User-Only - Exclusive Time

  3. 1. Observing Program-OS InteractionExample 1: "Interrupts” (Interrupts induced by large number of icmp pings) NAS Parallel Benchmark SP Class W run with and without interrupts User-Only Inclusive Time View User-Only Exclusive Time View Approx. 16 secs dilation in MPSP() Exclusive Time. Why? Approx. 25 secs dilation in Total Inclusive Time. Why? Application Profile does not tell the whole story!

  4. 1. Observing Program-OS InteractionExample 1: "Interrupts” (Interrupts induced by large number of icmp pings) Merged Inclusive Time View Merged Exclusive Time View MPSP excl. time difference only 4 secs. Excl-time view clearly identifies the culprits. 1. schedule() 2. do_IRQ() 3. icmp_reply() 4. do_softirq() Pings cause interrupts (do_IRQ). Which in turn handled after interrupt by soft-interrupts (do_softirq). Actual routine is icmp_reply/rcv. Large number of softirqs causes ksoftirqd to be scheduled-in, causing SP to be scheduled-out. Kernel-Space Time Taken by: 1.do_softirq() 2. schedule() 3. do_IRQ() 4. sys_poll() 5. icmp_rcv() 6. icmp_reply()

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