Messages in this thread | | | Date | Sat, 21 Sep 2002 16:15:10 +0200 | From | Manfred Spraul <> | Subject | Re: quadratic behaviour |
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> Let me repeat this, and call it an observation instead of a question, > so that you do not think I am in doubt. > > If you have 20000 processes, and do ps, then get_pid_list() will be > called 1000 times, and the for_each_process() loop will examine > 10000000 processes. > > Unlike the get_pid() situation, which was actually amortized linear with a very > small coefficient, here we have a bad quadratic behaviour, still in 2.5.37. > One solution would be to replace the idtag hash with an idtag tree.
Then get_pid_list() could return an array of sorted pids, and finding the next pid after unlocking the task_lock would be just a tree lookup (find first pid larger than x).
And a sorted tree would make it possible find the next safe range for get_pid() with O(N) instead of O(N^2).
-- Manfred
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