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SubjectRe: [patch] lockless, scalable get_pid(), for_each_process() elimination, 2.5.35-BK
It's also not a bad idea to sometimes say "Linux cannot do that".  Trying
to make the system do _everything_ will result in it doing many things very
poorly.

} Again, you're talking about entirely theoretical numbers that have no
} relevance for real life.
}
} Sure, you can do that. But a real life box? Nope.
}
} > Or in 1.25 hours
} > on an 8-way box. And then we are back to step #1: trying to pass over
} > already allocated PIDs by destroying the contents of the L1 and L2 cache
} > once for each allocated PID passed.
}
} So? It happens very rarely, and..
}
} > Sure, with 2 billion PIDs space that
} > averages out, but it's an algorithm with a very nasty worst-case behavior,
} > which is not so hard to trigger.
}
} ... the worst-case-behaviour is basically impossible to trigger with any
} real load.
}
} The worst case does not happen for "100k threads" like you've made it
} sound like.
}
} The worst case happens for "100k threads consecutive in the pid space".
}
} Which means that not only do you have to roll over, you have to roll over
} with a humungous number of threads _still_ occupying their old consecutive
} positions when you roll over.
}
} I repeat: you're making up schenarios that simply have no relevance to
} real life.
}
} Linus
}
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