| Steve's Networked Programming
Newsletter |
Making Nets
Work
February
2010
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Happy
2010! ACE is back in the spotlight this month for a
couple of reasons you may be interested
in.
First, I'm completing some performance
improvements for ACE_Dev_Poll_Reactor on behalf of a
long-time customer. How this came to be is
illustrative.
Second, Riverace put a new set of
ACE support service plans in place for 2010. I'll
explain more below, but the short story is we're
"kickin' it up a notch."
As always, be sure to forward this note to other
people you work with to be sure they know what's
happening in the world of networked application
development.
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Improving
ACE_Dev_Poll_Reactor Performance: Why?
How?
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A few
weeks ago I got a call from a long-time customer who
runs a performance-intensive system based on ACE
that relies on high-volume data routing and processing.
As demands on the system have grown it has scaled up
nicely. However, they recently began to notice a
performance limit they believed to be related to
ACE_TP_Reactor. This customer wanted me to investigate
this issue and help to resolve it.
After studying
source code together, I suspected that ACE_TP_Reactor
had some fairness issues. Under load with many network
connections, ACE_TP_Reactor didn't always service all
connections evenly; some got more attention, while
others starved. I wrote a test program to verify this
suspicion and it was confirmed.
After working to
improve the fairness I came to the conclusion that
really resolving this issue would probably involve some
significant design changes to ACE_TP_Reactor. So I
huddled with the customer's team to discuss the best way
to resolve the performance problem. This particular
system runs on Linux, so we discussed the possibility of
using ACE_Dev_Poll_Reactor instead; the concurrency
characteristics of the two reactor implementations are
the same starting at ACE 5.7, so switching would not
involve a programming change in the current event
handler design. The questions were then 1) Is
ACE_Dev_Poll_Reactor more fair to network connections
than ACE_TP_Reactor, and 2) How to resolve a known
performance issue with
ACE_Dev_Poll_Reactor?
Hooking
ACE_Dev_Poll_Reactor up to my new fairness test answered
the first question quickly: ACE_Dev_Poll_Reactor showed
excellent fairness under load. The performance, however,
was a problem. I did some initial work to reduce the
number of times the reactor token needed to be acquired
while processing notifications. That improved the
situation some, but not sufficiently. I then designed
more changes to reduce thread thrashing on the reactor
token, which is the root cause of the performance
problems. You can read more of the technical details in
a related blog
article. The benefits to my customer will be that 1)
their system's performance will increase noticeably, and
2) they'll be certain that the ACE changes really solve
their performance issues because I worked with them to
verify the results along the way. The rest of the ACE
community will also benefit from the improved
performance.
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| New,
Improved ACE Professional Support Services |
Riverace
introduced an improved suite of ACE Professional Support
services in January. The new services are designed to
improve service by:
- Lengthening the support horizon for ACE releases
from 1 year to 5 years
- Ensuring that in-demand computing platforms are
maintained and developed in a more equitable fashion
- Allowing Riverace to focus intently on providing
improved service levels for customers who rely on
Riverace for supporting applications in the field as
well as for those developing new, leading-edge
systems.
The previous 3-tier (Stream, River,
Whitewater) by 2-level (Group, per-developer) service
offering is replaced by a 2-tier (Development,
Enterprise) arrangement that's delivered by platform
rather than by group size. For complete details on the
new service offerings, please see http://www.riverace.com/ace/ace_support_plans.htm.
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| Do You
Need Help Designing Your Next System? |
Nobody
has to tell you that designing a well-formed, efficient,
maintainable networked application is hard. You've had
to deal with it. The problem is that networking
functionality is usually in a supporting role to your
system's main purposes, and your skills and experience
are much better used to focus on specific business and
technology issues. It may make more sense to bring in
seasoned expertise to help design a solid networking
base in your next system.
I've helped many
companies get great networked applications built - I may
be able to help you as well. Let's talk and see if I can
help take care of the networking, and let you focus on
applying your expertise and experience to the business
features that'll really help your system stand
out.
Call me at 508-541-9180 or email me at shuston@riverace.com.
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If you have any ideas for areas of networked
programming you'd like to hear about in future issues,
please email me with your suggestions. In the meantime,
keep those nets working!
Sincerely,
Steve Huston
Riverace
Corporation
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