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

ClamXav 2.15.2 - Virus checker based on...
ClamXav is a popular virus checker for OS X. I have been working on ClamXav for more than 10 years now, and over those years, I have invested a huge amount of my own time and energy into bringing... Read more
TechTool Pro 9.5.3 - 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
Safari Technology Preview 11.1 - The new...
Safari Technology Preview contains the most recent additions and improvements to WebKit and the latest advances in Safari web technologies. And once installed, you will receive notifications of... Read more
Google Chrome 61.0.3163.91 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
Dropbox 35.4.20 - Cloud backup and synch...
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
GraphicConverter 10.5 - $39.95
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
Chromium 61.0.3163.91 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 61.0.3163.91: Release notes were unavailable... Read more
Vitamin-R 2.50 - Personal productivity t...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more
XMind 8 Update 4 - Popular mind mapping...
XMind is the most popular mind mapping tool. Millions of people use XMind to clarify thinking, manage complex information, run brainstorming and get work organized. It couldn't be easier to get... Read more
Direct Mail 5.0.1 - Create and send grea...
Direct Mail is an easy-to-use, fully-featured email marketing app purpose-built for macOS. Create, send, and track great looking email campaigns that get results. Start your newsletter by selecting... Read more

Phoenix Wright: Ace Attorney - Spirit of...
Phoenix Wright: Ace Attorney - Spirit of Justice 1.00.00 Device: iOS Universal Category: Games Price: $.99, Version: 1.00.00 (iTunes) Description: ************************************************※IMPORTANT※・Please read the “When... | Read more »
Kpressor (Utilities)
Kpressor 1.0.0 Device: iOS Universal Category: Utilities Price: $4.99, Version: 1.0.0 (iTunes) Description: The ultimate ZIP compression application for iPhone and iPad. - Full integration of iOS 11 with support for multitasking.-... | Read more »
Find out how you can save £35 and win a...
Nothing raises excitement like a good competition, and we’re thrilled to announce our latest contest. We’ll be sending one lucky reader and a friend to the Summoners War World Arena Championship at Le Comedia in Paris on October 7th. It’s the... | Read more »
Another Lost Phone: Laura's Story...
Another Lost Phone: Laura's Story 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Another Lost Phone is a game about exploring the social life of a young woman whose phone you have just... | Read more »
The Witness (Games)
The Witness 1.0 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0 (iTunes) Description: You wake up, alone, on a strange island full of puzzles that will challenge and surprise you. You don't remember who you are, and... | Read more »
Egg, Inc. guide - how to build your gold...
Egg, Inc.'s been around for some time now, but don't you believe for one second that this quirky clicker game has gone out of style. The game keeps popping up on Reddit and other community forums thanks to the outlandish gameplay (plus, the... | Read more »
The best deals on the App Store this wee...
Good news, everyone! Your favorite day of the week has arrived at last -- it's discount roundup day! This fine Wednesday evening we're gathering up the hottest deals on the App Store. We've got action platformers, we've got puzzle games, we've got... | Read more »
Morphite (Games)
Morphite 1.08 Device: iOS Universal Category: Games Price: $7.99, Version: 1.08 (iTunes) Description: | Read more »
Fitness AR (Healthcare & Fitness)
Fitness AR 0.1.1 Device: iOS Universal Category: Healthcare & Fitness Price: $2.99, Version: 0.1.1 (iTunes) Description: Explore your Strava bike rides and runs in augmented reality. A beautiful 3D terrain map, powered by Mapbox... | Read more »
ARise (Games)
ARise 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: **ARKit only Puzzle game****Chapter 1 available now - More worlds coming soon!** ARise is an experience about perspective. Using the AR... | Read more »

Price Scanner via MacPrices.net

OWC USB-C Travel Dock with 5 Ports Connectivi...
OWC have announced the new OWC USB-C Travel Dock, the latest addition to their line of connectivity solutions. The USB-C Travel Dock lets you connect its integrated USB-C cable to a Mac or PC laptop... Read more
Pelican Products, Inc. Unveils Cases For All...
Pelican Products, Inc. has announced the launch of its full line of cases including Voyager, Adventurer, Protector, Ambassador, Interceptor (for the Apple iPhone 8 and 8 Plus backwards compatible... Read more
$100 off new 2017 13-inch MacBook Airs
B&H Photo has 2017 13″ MacBook Airs on sale today for $100 off MSRP including free shipping. B&H charges NY & NJ sales tax only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off... Read more
Apple restocks Certified Refurbished 13-inch...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $719 and 2016 models available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Is iPhone X Really The Future Of The Smartpho...
Should iPhone X even be called a telephone? It does of course support telephony and texting, but its main feature set is oriented to other things. It is also debatable whether it makes any rational... Read more
OtterBox Announces Full Case Lineup for iPhon...
Apple revolutionized the smartphone industry 10 years ago with the original iPhone, and OtterBox has set the standard of protection from the very beginning by protecting every generation of iPhone.... Read more
LifeProof Introduces What’s NEXT Cases for iP...
LifeProof built its reputation on sleek, ultra-protective iPhone cases. From 360-degree coverage to the first screenless waterproof case, the protection pioneer has always pushed the limits.... Read more
Apple Refurbished 2016 15-inch MacBook Pros a...
Apple has Certified Refurbished 2016 15″ Touch Bar MacBook Pros available starting at $1949. An Apple one-year warranty is included with each model, and shipping is free: – 15″ 2.7GHz Touch Bar Space... Read more
Wednesday deal: 15-inch MacBook Pros for up t...
B&H Photo has 2017 15″ MacBook Pros on sale for $150-$200 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray: $2199, $200 off MSRP... Read more
2.6GHz Mac mini on sale for $599, $100 off MS...
B&H Photo has the 2.6GHz Mac mini (MGEN2LL/A) on sale for $599 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more

Jobs Board

Full time *Apple* Hardware Tech needed - ma...
…high level of attention to detail Ethics, integrity and trust Be a geek & Previous Apple experience a must. Previous Apple Retail or other Apple Specialist Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
*Apple* Store - Technical Specialist - Apple...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
*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* News Product Marketing Mgr., Publish...
Job Summary The Apple News Product Marketing Manager will work closely with a cross-functional group to assist in defining and marketing new features and services. Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.