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Date: Thu, 26 Sep 2002 01:36:10 -0700
From: William Lee Irwin III <wli@holomorphy.com>
To: Con Kolivas <conman@kolivas.net>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
       Rik van Riel <riel@conectiva.com.br>
Subject: Re: Useful fork info? WAS Re: [BENCHMARK] fork_load module tested for contest
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On Thu, Sep 26, 2002 at 12:57:16PM +1000, Con Kolivas wrote:
> fork_load:
> Kernel                  Time            CPU             Ratio
> 2.4.19                  97.11           67%             1.33
> 2.4.19-ck7              72.34           92%             0.99
> 2.5.38                  75.32           92%             1.03
> 2.5.38-mm2              74.99           92%             1.03
> 2.4.19: Children forked: 32750
> 2.4.19-ck7: Children forked: 6477
> 2.5.38: Children forked: 5545
> 2.5.38-mm2: Children forked: 5351
> You can see clearly repeatedly forking a new process significantly slows down
> compile time for 2.4.19 but not the O(1) based kernels. However, the number of
> processes that are forked is significantly reduced.
> Is this information useful? 

Well, it means something. I should point out that the cost of pagetable
copying is increased by pte-based reverse mapping, and your "children
forked" throughput results reflect this. It's a known issue, and AFAIK
regarded as a reasonable tradeoff.

Cheers,
Bill
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