Kay Sievers wrote:
On Thu, May 28, 2009 at 16:35, Alan Jenkins <alan-jenkins@xxxxxxxxxxxxxx> wrote:
Now available for your delight and/or horror.
<http://github.com/sourcejedi/udev/commits/threading-v0.3>
For now, I'm still treating this as a patch series. That is, I may
publish future versions with a rewritten history. I'll preserve the old
branches though.
It turns out the MADV_DONTFORK hack I was so proud of is
implementation-dependant, i.e. a dirty hack. However, I'm confident
that glibc can and should be modified to do it for all programs. And it
is so worth it. On my test machine, threading alone goes from 2s
boot-time coldplug to 1.3-ish. MADV_DONTFORK takes it down to 0.7-ish.
The hack is contained in the last patch, "when forking a program, only
copy the stack of the _current_ thread".
Is that a single or dual CPU box?
With the threaded version, it's 0.18 (1.51 -> 1.33) seconds faster
here for a full coldplug run on a:
Intel(R) Core(TM)2 Duo CPU U9400 @ 1.40GHz.
It might be that the threaded version will only behave that much
better on a single CPU machine?
No, it's not that. I'm afraid the result of ~0.7 seconds result was an
accident; the bootchart looks suspicious and it didn't obtain when I
retested. The "fixed" version of the last patch doesn't work, and I
don't think it can.
The version that crashed on boot may be useful for comparison purposes
though. I will try and see how much I can reduce the page fault
overhead without using threads. Maybe just recycling the event
processes would bring similar gains, with less of the risks of threads.
Alan
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