Hi.
On 20.07.2012 22:38, Adrian Chadd wrote:
I'm worried that this won't be the only source of "freebsd is slower
than linux" issues.
What can we add to the timer path to make identifying and root causing
this issue easy? I'd just like to be absolutely sure that we're not
only doing the best job possible, but we can provide some tools and
statistics to the user/administrator so as to make debugging much
easier.
The only instrument to diagnose this problem without provided input I
could propose is hwpmc profiling. It should be able to show that we are
spending much time in those timer routines. If we guessed somehow that
reason is in slow ACPI timer, it is easy to write respective benchmark,
but we can't write tests for everything, and even if we could, users
won't be able to run/analyze output of them without some level of knowledge.
I've spent much time profiling that on hardware I have, but the only way
to be sure in general case I see is more testing and feedbacks. For this
specific area I am using very simple test, that effectively depends on
interrupt latency and CPUs wakeup times: `dd if=/dev/ada0 of=/dev/null
bs=512`. Depending on device, controller and other factors, gives me
about 20-30K IOPS.
If you have some ideas what and how could we test automatically -- welcome.
--
Alexander Motin
_______________________________________________
freebsd-stable@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-stable
To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
