From: Cort Dougan <cort@fsmlabs.com>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Ingo Molnar <mingo@elte.hu>, Rik van Riel <riel@conectiva.com.br>,
Andries Brouwer <aebr@win.tue.nl>,
William Lee Irwin III <wli@holomorphy.com>,
linux-kernel@vger.kernel.org
Subject: Re: [patch] lockless, scalable get_pid(), for_each_process() elimination, 2.5.35-BK
Date: Wed, 18 Sep 2002 11:35:51 -0600 [thread overview]
Message-ID: <20020918113551.A654@host110.fsmlabs.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0209181026550.1230-100000@home.transmeta.com>; from torvalds@transmeta.com on Wed, Sep 18, 2002 at 10:30:35AM -0700
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
}
} -
} 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/
next prev parent reply other threads:[~2002-09-18 17:33 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-17 23:06 [patch] lockless, scalable get_pid(), for_each_process() elimination, 2.5.35-BK Ingo Molnar
2002-09-18 0:22 ` William Lee Irwin III
2002-09-18 1:27 ` David S. Miller
2002-09-18 2:22 ` William Lee Irwin III
2002-09-18 10:11 ` Ingo Molnar
2002-09-18 14:28 ` William Lee Irwin III
2002-09-18 12:32 ` Andries Brouwer
2002-09-18 12:56 ` Ingo Molnar
2002-09-18 16:17 ` Linus Torvalds
2002-09-18 16:46 ` Ingo Molnar
2002-09-18 16:57 ` Ingo Molnar
2002-09-18 18:28 ` Andries Brouwer
2002-09-18 18:27 ` William Lee Irwin III
2002-09-18 19:00 ` Ingo Molnar
2002-09-18 20:11 ` Andries Brouwer
2002-09-18 20:29 ` William Lee Irwin III
2002-09-18 21:15 ` Andries Brouwer
2002-09-19 3:05 ` Ingo Molnar
2002-09-19 13:11 ` Andries Brouwer
2002-09-21 12:56 ` quadratic behaviour Andries Brouwer
2002-09-21 17:06 ` Linus Torvalds
2002-09-21 17:35 ` William Lee Irwin III
2002-09-21 17:49 ` Ingo Molnar
2002-09-21 17:46 ` William Lee Irwin III
2002-09-18 14:49 ` [patch] lockless, scalable get_pid(), for_each_process() elimination, 2.5.35-BK William Lee Irwin III
2002-09-18 15:01 ` Cort Dougan
2002-09-18 15:33 ` Ingo Molnar
2002-09-18 15:31 ` yodaiken
2002-09-18 15:35 ` Cort Dougan
2002-09-18 15:37 ` Rik van Riel
2002-09-18 15:50 ` Alan Cox
2002-09-18 18:31 ` Andries Brouwer
2002-09-18 18:32 ` William Lee Irwin III
2002-09-18 16:15 ` Linus Torvalds
2002-09-18 16:32 ` Rik van Riel
2002-09-18 16:48 ` Linus Torvalds
2002-09-18 17:31 ` Ingo Molnar
2002-09-18 21:46 ` Rogier Wolff
2002-09-18 16:41 ` Ingo Molnar
2002-09-18 16:45 ` William Lee Irwin III
2002-09-18 16:59 ` Linus Torvalds
2002-09-18 17:36 ` Ingo Molnar
2002-09-18 17:36 ` William Lee Irwin III
2002-09-18 17:46 ` Linus Torvalds
2002-09-18 17:47 ` William Lee Irwin III
2002-09-18 17:59 ` Ingo Molnar
2002-09-18 17:50 ` William Lee Irwin III
2002-09-18 18:07 ` Ingo Molnar
2002-09-19 19:27 ` Martin Mares
2002-09-17 15:31 ` Pavel Machek
2002-09-19 20:07 ` Richard B. Johnson
2002-09-18 16:46 ` Rik van Riel
2002-09-18 16:53 ` Linus Torvalds
2002-09-18 17:00 ` Rik van Riel
2002-09-18 17:16 ` Linus Torvalds
2002-09-18 17:28 ` Ingo Molnar
2002-09-18 17:38 ` Ingo Molnar
2002-09-18 17:24 ` Ingo Molnar
2002-09-18 17:30 ` Linus Torvalds
2002-09-18 17:35 ` Cort Dougan [this message]
2002-09-18 17:43 ` Rik van Riel
2002-09-18 17:48 ` Martin J. Bligh
2002-09-18 17:57 ` Cort Dougan
2002-09-18 18:08 ` Martin J. Bligh
2002-09-18 18:28 ` Ingo Molnar
2002-09-18 18:33 ` Linus Torvalds
2002-09-18 18:51 ` Ingo Molnar
2002-09-18 18:56 ` interruptible_sleep_on_timeout() and signals Imran Badr
2002-09-19 7:16 ` David Woodhouse
2002-09-18 19:53 ` [patch] lockless, scalable get_pid(), for_each_process() elimination, 2.5.35-BK Martin J. Bligh
2002-09-22 0:34 ` Andrea Arcangeli
2002-09-22 10:02 ` Ingo Molnar
2002-09-22 15:27 ` Andrea Arcangeli
2002-09-18 18:02 ` Ingo Molnar
2002-09-18 17:58 ` Cort Dougan
2002-09-18 18:14 ` Ingo Molnar
2002-09-18 17:54 ` Alan Cox
2002-09-18 17:54 ` Ingo Molnar
2002-09-18 18:00 ` yodaiken
2002-09-18 18:21 ` Ingo Molnar
2002-09-18 18:33 ` yodaiken
2002-09-18 16:55 ` Alan Cox
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