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 iMovie 10.1.6 - Edit personal vide...
With an all-new design, Apple iMovie lets you enjoy your videos like never before. Browse your clips more easily, instantly share your favorite moments, and create beautiful HD movies and Hollywood-... Read more
TechTool Pro 9.5.1 - Hard drive and syst...
TechTool Pro has long been one of the foremost utilities for keeping your Mac running smoothly and efficiently. With the release of version 9, it has become more proficient than ever. TechTool... Read more
Jamf Pro 9.99.0 - Powerful sysadmin/ente...
Jamf Pro (formerly Casper Suite) is the EMM tool that delights IT pros and the users they support by delivering on the promise of unified endpoint management for Apple devices. At Jamf, connecting... Read more
VueScan 9.5.78 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Adobe Lightroom 6.10.1 - Import, develop...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
iPhoto Library Manager 4.2.7 - Manage mu...
iPhoto Library Manager allows you to organize your photos among multiple iPhoto libraries, rather than having to store all of your photos in one giant library. You can browse the photos in all your... Read more
Smultron 9.4 - Easy-to-use, powerful tex...
Smultron 9 is an elegant and powerful text editor that is easy to use. Use it to create or edit any text document. Everything from a web page, a note or a script to any single piece of text or code.... Read more
TextSoap 8.4 - Automate tedious text doc...
TextSoap can automatically remove unwanted characters, fix up messed up carriage returns, and do pretty much anything else that we can think of to text. Save time and effort. Be more productive. Stop... Read more
Merlin Project 4.2.3 - $349.00
Merlin Project is the leading professional project management software for OS X. If you plan complex projects on your Mac, you won’t get far with a simple list of tasks. Good planning raises... Read more
QuarkXPress 13.0.0.0 - Desktop publishin...
QuarkXPress 2017 is the new version that raises the bar for design and productivity. With non-destructive graphics and image editing directly within your layout, you no longer have to choose between... Read more

Latest Forum Discussions

See All

Goat Simulator PAYDAY (Games)
Goat Simulator PAYDAY 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: ** IMPORTANT - SUPPORTED DEVICES **iPhone 4S, iPad 2, iPod Touch 5 or better Goat Simulator: Payday is the most... | Read more »
Zombie Gunship Survival Beginner's...
The much anticipated Zombie Gunship Survival is here. In this latest entry in the Zombie Gunship franchise, you're tasked with supporting ground troops and protecting your base from the zombie horde. There's a lot of rich base building fun, and... | Read more »
Mordheim: Warband Skirmish (Games)
Mordheim: Warband Skirmish 1.2.2 Device: iOS Universal Category: Games Price: $3.99, Version: 1.2.2 (iTunes) Description: Explore the ruins of the City of Mordheim, clash with other scavenging warbands and collect Wyrdstone -... | Read more »
Mordheim: Warband Skirmish brings tablet...
Legendary Games has just launched Mordheim: Warband Skirmish, a new turn-based action game for iOS and Android. | Read more »
Magikarp Jump splashes onto Android worl...
If you're tired ofPokémon GObut still want something to satisfy your mobilePokémon fix,Magikarp Jumpmay just do the trick. It's out now on Android devices the world over. While it looks like a simple arcade jumper, there's quite a bit more to it... | Read more »
Purrfectly charming open-world RPG Cat Q...
Cat Quest, an expansive open-world RPG from former Koei-Tecmo developers, got a new gameplay trailer today. The video showcases the combat and exploration features of this feline-themed RPG. Cat puns abound as you travel across a large map in a... | Read more »
Jaipur: A Card Game of Duels (Games)
Jaipur: A Card Game of Duels 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: ** WARNING: iPad 2, iPad Mini 1 & iPhone 4S are NOT compatible. ** *** Special Launch Price for a limited... | Read more »
Subdivision Infinity (Games)
Subdivision Infinity 1.03 Device: iOS Universal Category: Games Price: $2.99, Version: 1.03 (iTunes) Description: Launch sale! 40% Off! Subdivision Infinity is an immersive and pulse pounding sci-fi 3D space shooter. https://www.... | Read more »
Clash of Clans' gets a huge new upd...
Clash of Clans just got a massive new update, and that's not hyperbole. The update easily tacks on a whole new game's worth of content to the hit base building game. In the update, that mysterious boat on the edge of the map has been repaired and... | Read more »
Thimbleweed Park officially headed to iO...
Welp, it's official. Thimbleweed Park will be getting a mobile version. After lots of wondering and speculation, the developers confirmed it today. Thimbleweed Park will be available on both iOS and Android sometime in the near future. There's no... | Read more »

Price Scanner via MacPrices.net

Huawei Unveils New ‘Business-Styled’ MateBook...
Huawei has introduced a trio of new MateBook laptops, expanding its mobile portfolio and building on its success in delivering attractive and powerful high-end devices. The company claims the HUAWEI... Read more
Deal! Gold 12-inch 1.2GHz Retina MacBook for...
Amazon has the 2016 Gold 12″ 1.2GHz Retina MacBook (MLHF2LL/A) on sale for $350 off MSRP for a limited time. Shipping is free: - 12″ 1.2GHz Gold Retina MacBook: $1249.99 $350 off MSRP We expect this... Read more
13-inch 2.0GHz MacBook Pros on sale for $100...
B&H has the non-Touch Bar 13″ 2.0GHz MacBook Pros in stock today and on sale for $100 off MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 13″ 2.0GHz MacBook Pro Space... Read more
15-inch 2.2GHz Retina MacBook Pro, Apple refu...
Apple has Certified Refurbished 2015 15″ 2.2GHz Retina MacBook Pros available for $1699. That’s $300 off MSRP, and it’s the lowest price available for a 15″ MacBook Pro. An Apple one-year warranty is... Read more
Apple refurbished 9-inch and 12-inch iPad Pro...
Apple has Certified Refurbished 9″ and 12″ Apple iPad Pros available for up to $160 off the cost of new iPads. An Apple one-year warranty is included with each model, and shipping is free: - 32GB 9″... Read more
Apple Certified Refurbished iMacs available f...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
Sale! 15-inch 2.6GHz Silver Touch Bar MacBook...
DataVision has the 15″ 2.6GHz Silver Touch Bar MacBook Pro (MLW72LL/A) on sale for $2199 including free shipping. Their price is $200 off MSRP, and it’s the lowest price available for this model (... Read more
A Kaby Lake Processor Upgrade For The MacBook...
Now they tell me! Well, actually Apple hasn’t said anything official on the subject, but last week Bloomberg News’s Mark Gurman and Alex Webb cited unnamed “people familiar with the matter”... Read more
Kodak’s Camera-First Smartphone EKTRA Launche...
The Eastman Kodak Company and Bullitt Group have announced the availability of a U.S. GSM version of the KODAK EKTRA Smartphone. The U.S. launch coincides with a software update addressing requests... Read more
Apple Launches App Development Curriculum for...
Apple today launched a new app development curriculum designed for students who want to pursue careers in the fast-growing app economy. The curriculum is available as a free download today from Apple... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Systems Engineer - California Polyte...
Cal Poly, San Luis Obispo Apple Systems Engineer Department: ITS - Customer & Tech Support (134900) College/Division: Academic Affairs Salary Range: Position Read more
Best Buy *Apple* Computing Master - Best Bu...
**508718BR** **Job Title:** Best Buy Apple Computing Master **Location Number:** 001526-Odessa-Store **Job Description:** **What does a Best Buy Apple Computing Read more
Data Engineer - *Apple* Media Products - Ap...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.