Messages in this thread | | | From | Bjorn Helgaas <> | Subject | boot-time slowdown for measure_migration_cost | Date | Fri, 27 Jan 2006 14:03:27 -0700 |
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The boot-time migration cost auto-tuning stuff seems to have been merged to Linus' tree since 2.6.15. On little one- or two-processor systems, the time required to measure the migration costs isn't very noticeable, but by the time we get to even a four-processor ia64 box, it adds about 30 seconds to the boot time, which seems like a lot.
Is that expected? Is the information we get really worth that much? Could the measurement be done at run-time instead? Is there a smaller hammer we could use, e.g., flushing just the buffer rather than the *entire* cache? Did we just implement sched_cacheflush() incorrectly for ia64?
Only ia64, x86, and x86_64 currently have a non-empty sched_cacheflush(), and the x86* ones contain only "wbinvd()". So I suspect that only ia64 sees this slowdown. But I would guess that other arches will implement it in the future.
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