How to decrease build times / speed up compile tim

Question

What strategies can be used in general to decrease build times for any XCode project? I'm mostly interested in XCode specific strategies.

I'm doing iPhone development using XCode, and my project is slowly getting bigger and bigger. I find the compile / link phases are starting to take more time than I'd like.

Currently, I'm:

• Using Static Libraries to make it so most of my code doesn't need to be compiled everytime I clean and build my main project

• Have removed most resources from my application, and test with a hard coded file system path in the iPhone simulator whenever possible so my resources don't have to constantly be packaged as I make changes to them.

I've noticed that the "Checking Dependencies" phase seems to take longer than I'd like. Any tips to decrease that as well would be appreciated!

Answer 1

Easy answer: add another machine running XCode on your local network. XCode incorporates distcc to do distributed compiles. It can even use Bonjour to find other build hosts, which simplifies the process of configuring this greatly. For large builds, distributing can get you a speed increase that is nearly linearly proportional to the number of build machines (2 machines takes half the time, three takes a third and so on).

To see how to set this up, you can consult this development doc. It also features other useful build time improvement strategies, such as using precompiled headers and predictive builds.

Edit: Sadly, it appears Apple has removed this feature as of Xcode 4.3: http://lists.apple.com/archives/xcode-users/2012/Mar/msg00048.html

Xcode 5 has a server version which can do CI, but I doubt this will confer any benefit for ad hoc developer builds. However, there are some unannounced features that should dramatically speed up build times.

Answer 2

I used a script to make use of a RAM drive, together with some "forward declarations" optimizations my project clean build time went from 53 seconds to 20 seconds.

I was tempted to get the Gui on the AppStore, but opted rather to go for command line. I put the script as part of git repository.

To see the build times, enter this in a terminal: "defaults write com.apple.dt.Xcode ShowBuildOperationDuration YES"

Restart Xcode to notice the build times in the toolbar. (this is my non clean build time using objective-c)

Adjust the script to your liking. - Note the script clears the derived data folder.

#!/bin/sh

#2 GIG RAM
GIGA_BYTES=$((2*1024*1024*1024))

# a sector is 512 bytes
NUMSECTORS=$((${GIGA_BYTES}/512))

#ram disk
mydev=`hdiutil attach -nomount ram://$NUMSECTORS`
newfs_hfs $mydev

# make mount point
MOUNT_POINT=/Users/your_user_name/Library/Developer/Xcode/DerivedData

# ******************************************* 
# ** WARNING - MOUNT POINT WILL BE DELETED ** 
# *******************************************
rm -rf ${MOUNT_POINT}
mkdir -p ${MOUNT_POINT}

# mount
mount -t hfs $mydev ${MOUNT_POINT}
echo unmount $(MOUNT_POINT)

To see the effect and to control the RAM Drive:

mount                       - see mount points
umount mount_point          - unmount point
diskutil list               - see disks
diskutil eject /dev/diskX   - eject the disk
df -ahl                     - see free space

NOTE: I essentially use the hdiutil provided by macOs. I tried switching the -kernel option (no swapping to disk) on but failed on my machine, saying it is not implemented.

Maybe the new OS coming soon we will see even more improvements as the new file system copy feature is really fast, and possibly makes this script redundant.

Answer 3

If you're not using 8GB of RAM, upgrade now.

I just upgraded my macbook pro from 4GB to 8GB. My project build time went from 2:10 to 0:45. I was floored by the improvement. It also makes web browsing for research snappier and general Xcode performance when indexing, etc.

Answer 4

If your whole project gets rebuilt every time you hit run, that's probably the bug in XCode 7.0 <= 8.1 giving you a hard time.

Creating the user defined build setting HEADERMAP_USES_VFS to YES cut the macbook compile time from 75 seconds each time, to 25 seconds. See Xcode 8 does full project rebuild for more info.

Answer 5

The number of threads Xcode will use to perform tasks defaults to the same number of cores your CPU has. For example, a Mac with an Intel Core i7 has two cores, so by default Xcode will use a maximum of two threads. Since compile times are often I/O-bound rather than CPU-bound, increasing the number of threads Xcode uses can provide a significant performance boost for compiles.

Try configuring Xcode to use 3, 4 or 8 threads and see which one provides the best performance for your use case.

You can set the number of processes Xcode uses from Terminal as follows:

defaults write com.apple.Xcode PBXNumberOfParallelBuildSubtasks 4

Please see Xcode User Defaults for more information.

Answer 6

One huge tip to halve compile times (for iOS projects at least) is to set Build Settings / Architectures / Build Active Architecture Only to YES.

What this does (especially with the advent of 64-bit iPads/64-bit compiler) is to not build the binary for the architectures you're not currently using.

Make sure you remember to re-enable this setting on submission to the app store, or your binary will not validate.