TweetFollow Us on Twitter

To Tune, or Not to Tune

Volume Number: 22 (2006)
Issue Number: 8
Column Tag: Tuning

To Tune, or Not to Tune

That is the Question

by Steve Modica

Welcome

One of the things I love about using a Mac is the way Apple supports their customers. Apple provides software and hardware to support the vast majority of their customers' needs. Their updates are reliable and simple, so that customers move to them quickly. As a result, I am typing this article on a system that is similar to 99% of all other Apple systems. If there is a bug lying in wait for me, chances are, someone else has discovered it, and the bug is fixed before I discover it. There is a lot to be said for strength in numbers.

Having spent many years supporting high performance computing customers, I have debugged many calls from customers who were quite sure they were not getting the best performance from their computers. In some cases; they were right! In most cases there were other factors that had nothing to do with system tuning. However, there is always this notion that some "wizard" can come along and wave his magic tuning wand, and for no additional investment, make your system go faster!

Sorting it Out

If you are a car mechanic, certainly, no one would tell you how to fix your car. There are experts who choose to change spark plug brands between summers and winters because they can detect a performance difference. Experts like these, also have the time, equipment, and experience to fix mistakes when they accidentally knock a hose off their engine while poking around. I'd like to refer to this as, "cars as a hobby." This is not about a need for a better-tuned car or a return on investment. It is about having fun working on your car and achieving perfection. These people are honing their art.

Like most PowerBooks, mine is a workhorse. It handles personal and business finances, email, web browsing, and various applications. There are gigabytes of data on there that are extremely important to my family, my business, and me. I don't believe my PowerBook is doing anything different from what Apple intended, nor do I need to tune it. There might be a 5% performance improvement somewhere if I tweak something here or there, but then my PowerBook is no longer like 99% of the other PowerBooks. But now, after making performance optimizations, my increased network performance or maximized disk performance puts me right at the front of the list for finding a hidden bug.

So when should you tune?

First, trying to tune a system that does not have the resources it requires to do the assigned job is like trying to tune a cheaply made guitar. If you are serious about getting work done, get a well-made guitar. Second, if the system's usage pattern is typical, do not tune your system. You are better off taking advantage of all the similarly configured systems doing the same thing that are tuned the same way. But if your system is being asked to do something special, like serving only really large video files, then perhaps tuning is something you may want to consider.

If you call the system your "mail server" or your "file server," then there is a good chance your system is doing a specific task much more often than a typical system. This is when you may find some benefit in tailoring the system configuration settings to that specific task.

Physical bottlenecks

Let's start by considering a fileserver. Assuming your Xserve or "repurposed" PowerMac is not quite making the grade as your fileserver. The first question you have to answer is:

Is this System Capable of Delivering the Performance I Need?

The best way to find this out is to first understand what your traffic looks like, and then break the problem down into easily measurable elements. Files must be read from disk into memory; memory must be turned into mbufs and routed onto the network. Depending on what client systems are doing, clients may need to pull data into memory and then store it to their local disk drives.

Your fileserver must have several resources to operate efficiently. Perhaps the most important resource is memory. Users tend to read the same data over and over again. Operating systems have long since taken this into account with the use of a buffer cache. A buffer cache is an area, set aside in memory, to store information temporarily. This is done so that the CPU can perform other tasks while the IO device fills up the buffer cache. The most recently read data is saved in memory so that it can be accessed quickly, without issuing a redundant read operation to the disk. Similarly, it is often the case that when we read the first byte of a file that we will continue to read many more bytes. Operating systems take this into account and perform read-ahead operations. This enables the operating system to have the data you need in memory even before you have requested it.

Assuming your system is equipped with ample resources; it is easy to isolate the physical limitations of the individual devices. For example, if you have 10 client systems retrieving data from a file server, and each client is achieving 90Mb/sec, then your aggregate network bandwidth is 900Mb/sec. This is the maximum bandwidth of a single Gigabit port. That is a very reasonable limitation. It follows then, that if you want better IO performance for your clients, you simply need to add additional Gigabit ports, and allocate these resources appropriately for each client. You may also see that your CPUs are at 100% utilization, or that your disk bandwidth is at its theoretical maximum throughput.

If you find that the system performs well at certain loads (1-3 clients), but begins to degrade drastically below its physical maximums as you add clients, then consider adding memory so that the operating system has more buffer cache to work with. It is very likely that you simply do not have enough memory, so that each client access requires a direct disk IO operation. If there is not enough memory for buffer cache or not enough memory for the operating system perform read-ahead operations, then disk IO operations become very inefficient.

One way to check how much memory is available for things like the Buffer Cache is to look at the Activity Monitor (Applications -> Utilities -> Activity Monitor). This utility allows the user to examine a number of system resources including CPU, memory and disk bandwidth. Looking at the System Memory pane, one can see how much memory the system is using. "Inactive" memory is memory that has been written out to disk, but is being kept around in case users attempt to access it again. Consider how much data each of your users is accessing and reusing continuously during an edit session. If a typical user is operating on 8GByte files and you have a few hundred MBytes of cached disk data, you probably do not have enough cache. Each time your users move around within their project, they are forcing the system to go back to disk, which creates a large number of inefficient IOs. Simply adding a few Gigabytes of memory will help performance immensely.

Why is it Sometimes Necessary To Tune Your Network?

Wouldn't it be great if somebody wrote a utility that analyzes your network and automatically selects the optimum settings? They already have! It's called TCP/IP, but occasionally it requires some attention. In most cases, TCP works remarkably well all by itself. Tuning is needed in cases where TCP is not optimized because the network behavior is not normal.

TCP/IP is not controlled by any manufacturer and is designed to work on almost any kind of underlying network with widely varying characteristics. To meet this challenge, the protocol designers made TCP adaptive. TCP is self monitoring and optimizes its own behavior to match the network environment. Adaptation takes time and the default settings cannot be optimized for every possible kind of network.

There are also many independent implementations, and the protocols continue to evolve in response to practical experience, and some implementations have peculiar compatibility constraints.

Typical network abnormalities are:

  • Asymmetric connections. These are connections that are much faster downstream, than upstream.
  • High performance connections with relatively long latency (measured in bytes) such as fiber optic, satellite, or point-to-point protocol (PPP) over a cellular network.
  • Point-to-point Protocol over Ethernet (PPPoE) implementations that restrict the maximum transmission unit (MTU) on the network without support for Path MTU Discovery or fragmentation.
  • Heavily congested links. Tuning cannot solve everything. You may need to restructure your network or use packet shaping to control traffic flows.

The key to optimization in such cases is to measure, adjust, and repeat. Notice that it's not necessary to find the perfect settings, only to get close enough that TCP works efficiently in your environment. The tools included with IPNetTunerX from Sustainable Softworks are designed to make this easy and show how well TCP is actually working. (Refer to http://sustworks.com for more information.) Keep it simple. IPNetTunerX offers a collection of presets to solve the most common tuning problems for users with asymmetric broadband connections.

The follow screen shot shows the Basic panel from IPNetTunerX. The Basic panel enables you to select presets that tune certain activities like connecting a Bluetooth phone or just browsing the internet.



Figure 1. IPNetTUnerX Basic Panel

The following screen shot shows the Advanced panel. The Advanced panel enables you to tune individual parameters like the TCP send and receive space.



Figure 2. IPNetTUnerX Advanced Panel

What if I have more than one kind of network connection, like wireless internet served through a satellite? Which one should I tune for?

Just as a chain is only as strong as its weakest link, you want to tune your connection to improve performance over the weakest link or bottleneck. If the connection is highly asymmetrical, has an MTU restriction, high latency, or some other problem, you make adjustments to compensate. The term tuning is misleading in this case because it suggests that you make adjustments to find the optimal setting. A "bottleneck bypass" is a better description. Getting around a bottleneck might reduce performance slightly in another area, but this usually isn't a problem.

Can I tune TCP differently for my Ethernet LAN versus Internet connection if they use different network ports?

TCP sits above the IP network layer so doesn't normally know how the underlying data is routed.

Can I tune TCP at my router, or do I need to tune TCP at each host on my LAN?

TCP is end-to-end, so it generally makes sense to tune TCP at one or both ends of the connection. Some devices offer a packet shaping feature that enables you to adjust TCP traffic flows to reduce congestion. Another possibility is to use a proxy server so that external connections originate from a different host. Depending on the problem, these might be appropriate but are generally more involved.


Steve Modica is CEO of Small Tree Communications, leading designer and manufacturer of high-performance network products for Mac OS X.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Apple iOS 9.3.5 - The latest version of...
iOS is the world’s most advanced mobile operating system, and it’s the foundation of iPhone, iPad, and iPod touch. It comes with a collection of apps and features that let you do the everyday things... Read more
Parallels Desktop 12.0.0 - Run Windows a...
Parallels allows you to run Windows and Mac applications side by side. Choose your view to make Windows invisible while still using its applications, or keep the familiar Windows background and... Read more
Spotify 1.0.36.124. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
Firefox 48.0.2 - Fast, safe Web browser.
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
BBEdit 11.6.1 - Powerful text and HTML e...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
OmniGraffle Pro 6.6.1 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
OmniGraffle 6.6.1 - Create diagrams, flo...
OmniGraffle helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use Graffle to... Read more
Dropbox 8.4.21 - Cloud backup and synchr...
Dropbox is an application that creates a special Finder folder that automatically syncs online and between your computers. It allows you to both backup files and keep them up-to-date between systems... Read more
BetterTouchTool 1.84 - Customize Multi-T...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
ScreenFlow 6.1 - Create screen recording...
ScreenFlow is powerful, easy-to-use screencasting software for the Mac. With ScreenFlow you can record the contents of your entire monitor while also capturing your video camera, microphone and your... Read more

Cartoon Network Superstar Soccer: Goal!!...
Cartoon Network Superstar Soccer: Goal!!! – Multiplayer Sports Game Starring Your Favorite Characters 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Become a soccer superstar with your... | Read more »
NFL Huddle: What's new in Topps NFL...
Can you smell that? It's the scent of pigskin in the air, which either means that cliches be damned, pigs are flying in your neck of the woods, or the new NFL season is right around the corner. [Read more] | Read more »
FarmVille: Tropic Escape tips, tricks, a...
Maybe farming is passé in mobile games now. Ah, but farming -- and doing a lot of a other things too -- in an island paradise might be a little different. At least you can work on your tan and sip some pina coladas while tending to your crops. [... | Read more »
Become the King of Avalon in FunPlus’ la...
King Arthur is dead. Considering the legend dates back to the 5th century, it would be surprising if he wasn’t. But in the context of real-time MMO game King of Avalon: Dragon Warfare, Arthur’s death plunges the kingdom into chaos. Evil sorceress... | Read more »
Nightgate (Games)
Nightgate 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: *** Launch Sale: 25% OFF for a limited time! *** In the year 2398, after a great war, a network of intelligent computers known as... | Read more »
3 best fantasy football apps to get you...
Last season didn't go the way you wanted it to in fantasy football. You were super happy following your drafts or auctions, convinced you had outsmarted everyone. You were all set to hustle on the waiver wire, work out some sweet trades, and make... | Read more »
Pokemon GO update: Take me to your leade...
The Team Leaders in Pokemon GO have had it pretty easy up until now. They show up when players reach level 5, make their cases for joining their respective teams, and that's pretty much it. Light work, as Floyd Mayweather might say. [Read more] | Read more »
Ruismaker FM (Music)
Ruismaker FM 1.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0 (iTunes) Description: Following up on the success of Ruismaker, here's her crazy twin-sister, designed for people who want to design their own... | Read more »
Space Marshals 2 (Games)
Space Marshals 2 1.0.15 Device: iOS iPhone Category: Games Price: $5.99, Version: 1.0.15 (iTunes) Description: The sci-fi wild west adventure in outer space continues with Space Marshals 2. This tactical top-down shooter puts you in... | Read more »
Dungeon Warfare (Games)
Dungeon Warfare 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: Dungeon Warfare is a challenging tower defense game where you become a dungeon lord to defend your dungeon against greedy... | Read more »

Price Scanner via MacPrices.net

BookBook Releases SurfacePad, BookBook &...
BookBook has released three new covers just for iPad Pro: SurfacePad, BookBook and BookBook Rutledge Edition. BookBook for iPad Pro is a gorgeous leather case reminiscent of a vintage sketchbook.... Read more
Clean Text 1.0 for iOS Reduces Text Cleanup a...
Apimac today announced availability of Clean Text for iOS, a tool for webmasters, graphic designers, developers and magazine editors to reduce text cleanup and editing time, and also for any iPhone... Read more
27-inch iMacs on sale for up to $220 off MSRP
B&H Photo has 27″ Apple iMacs on sale for up to $200 off MSRP including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2099 $200 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $1899 $100... Read more
Apple refurbished 13-inch MacBook Airs availa...
Apple has Certified Refurbished 2016 and 2015 13″ MacBook Airs now available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2016 13″ 1.6GHz/8GB/... Read more
Apple refurbished iPad mini 2s available for...
Apple is offering Certified Refurbished iPad mini 2s for up to $80 off the cost of new minis. An Apple one-year warranty is included with each model, and shipping is free: - 16GB iPad mini 2 WiFi: $... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more
Mac Pros on sale for $200 off MSRP
B&H Photo has Mac Pros on sale for $200 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3799, $200... Read more
Will We See A 10.5″ iPad Pro in 2017? – The ‘...
A MacRumors report, cites a research note from KGI Securities analyst Ming-Chi Kuo, saying a new size iPad model is in the works. According to the highly respected Cho, who has a strong track record... Read more
IOGEAR USB-C Docking Station Transforms Lapto...
IOGEAR has announced the launch of its innovative USB-C Docking Station with Power Delivery which turns USB-C enabled laptops into desktop workstations. The new IOGEAR USB-C Docking Station features... Read more
12-inch Retina MacBooks on sale for up to $10...
Amazon has 2016 12″ Apple Retina MacBooks on sale for $100 off MSRP. Shipping is free: - 12″ 1.1GHz Space Gray Retina MacBook: $1199 $100 off MSRP - 12″ 1.1GHz Silver Retina MacBook: $1224.99 $75 off... Read more

Jobs Board

*Apple* Professional Learning Specialist - A...
# Apple Professional Learning Specialist Job Number: 51234243 Portland, Maine, Maine, United States Posted: Aug. 18, 2016 Weekly Hours: 40.00 **Job Summary** The Read more
*Apple* Mobile Master - Best Buy (United Sta...
What does a Best Buy Apple Mobile Master do? At Best Buy, our mission is to leverage the unique talents and passions of our employees to inspire, delight, and enrich Read more
*Apple* Retail - Multiple Positions Akron, O...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Simply Mac *Apple* Specialist- Repair Techn...
…The Technician is a master at working with our customers to diagnose and repair Apple devices in a manner that exceeds the expectations set forth by Apple Read more
*Apple* Retail - Multiple Positions Germanto...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.