Le 6 sept. 07 à 15:12, Fabien THOMAS a écrit :
Hi,
After many years of good services we will stop using FreeBSD 4.x :)
During my performance regression tests under FreeBSD 6.2 i've found
that polling has lower performance than interrupt.
To solve that issue i've rewritten the core of polling to be more
SMP ready.
You can find a summary of all my tests and the source code at the
following address:
http://www.netasq.com/opensource/pollng-rev1-freebsd.tgz
Feel free to ask more detailed information if necessary and report
any bugs / comments.
Hello Fabien,
1- I have noticed you are not using GENERIC config file, can you
provide us more information on how your KERNCONF differs from
GENERIC ? I am pretty sure you have removed all the debug OPTIONs
from the kernel, isn't it ?
2- Did you get a chance to try Jumbo Frames and evaluate jumbo mbufs
(I never success to make them work for me, did someone had more
chance ?). In any cases, PPS values are important for such tests.
Andre is right, with Fast Forward you get the best perfs for such test.
3- Did you monitor the DUT to see where CPU cycles were spend in each
test ?
4- Have you considered measuring the time it takes for an interrupt
to be handled and processed by the kernel Bottom/Top Half and ISR ? [1]
5- When I have performed some test using a Spirent SmartBits
(SmartFlow) last summer I got the following results [2]. (For
comparison purposes)
6- In the test with Spirent Avalanche, you are using Lighttpd as
webserver, did you enable kqueue ? how many workers ?
You are using HTTP 1.0 wo Keep-Alive, what was your net.inet.tcp.msl
MIB's value ?
7- Polling is known to introduce higher latency, I would expect its
benefits to be less in 7-CURRENT compared to 6.x since (Scott ?) a
FAST INTR Handler has been introduced around a year ago. Nonetheless,
what you report sounds like a perf regression... Have you filled a
PR ? Luigi might have a good explaination here. :-D
8- Lock profiling information were obtanied through KTR ?
9- I was wondering if you have explored Intr CPU affinity [3] and IRQ
Swizzling [4] ?
Thanks for your efforts and your valuable contribution, best regards,
/Olivier
[1] http://xview.net/papers/interrupt_latency_scheduler/ (WARNING:
Never find the time to finish that doc and publish it) &&
http://xview.net/research/RTBench/
[2] http://xview.net/papers/jumbo_mbufs_freebsd/
[3] http://www.intel.com/cd/ids/developer/asmo-na/eng/188935.htm?prn=Y
[4] http://download.intel.com/design/chipsets/applnots/31433702.pdf
--
Olivier Warin
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