Kay Sievers wrote:
On Mon, May 25, 2009 at 15:46, Alan Jenkins <alan-jenkins@xxxxxxxxxxxxxx> wrote:
I solved one of the reservations that held me back on threaded udevd. I
still have some other concerns to work on, but I'm feeling much more
optimistic now.
Replacing processes with threads reduced page faults (copy-on-write) by
60-80%, but that _still_ left over 10% of udevd time in page fault overhead.
I've discovered I can reduce this overhead much further by marking thread
stacks with MADV_DONTFORK. When a thread needs to fork an external program,
it can temporarily unmark its own thread stack.
Disclaimer: I have no idea why this should reduce the number of page faults.
I could be getting something horribly wrong. But even if it's wrong, at
least it gives me a new angle on this problem.
Do you have numbers for the difference of threaded vs. non-threaded, for:
time (udevadm trigger; udevadm settle)
when no rules are active?
On my box it's ~0.6 seconds for the non-threaded udevd and ~460
devices, when I move all rules out of the way.
Thanks,
Kay
Interesting question. I stop HAL first, it tends to slow my tests down
and doesn't represent normal bootup.
Test machine is eeepc 701; trigger -n shows 382 devices.
no threading: ~0.5s
threading: ~0.25s
This is based on an a slightly out of date tree. Your latest HEAD is
still ~0.5s, but perhaps slightly lower, 0.46-0.48 as opposed to 0.48-0.5.
Alan
--
To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
