Instruments

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Instruments is a performance-analysis and testing tool for iOS, iPadOS, watchOS, tvOS, and macOS apps.

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Instruments in Xcode 15.3 not showing symbols
When using Instruments in Xcode 15.3 on macOS Sonoma 14.3.1 symbols from system frameworks are not displaying. I've tried creating a template "App" project and running it on the iOS 17.4 simulator without any code changes and still am not seeing symbols so I can be sure it's not unique to my real-world project build settings. If I install Xcode 15.0 and run the same build in the same 17.4 simulator using Instruments 15.0 it shows thread names and symbols for UIKit and other frameworks but is still missing SwiftUI symbols. Instruments 15.3 Instruments 15.0 I've spent 2 days trying to narrow down why I couldn't debug my app and even deleted all my partitions and reinstalled macOS which didn't fix the issue.
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1.3k
Mar ’24
os_signpost not working on macOS device, works on iOS device
I have an iOS app that uses os_signpost API for instrumentation. When I profile it from Xcode on real iOS device, it works as expected. When I profile its macCatalyst variant (using the identical code) on the same Mac where Xcode is running, the os_signpost Instrument does not show anything, not even the Apple provided signposts that are otherwise visible on the iOS. How do I make it work?
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939
May ’24
An address of the top frame's IP is always off by 1 in *-profile tables
Hi! Is there a reason why trace's *-profile tables (time-profile, cpu-profile, counters-profile) always use an instruction pointer value that is 1 byte larger than what should be a true instruction pointer value? Odd valued IPs on Apple M2 are definitely incorrect as instructions have to be word-aligned. It's also worth mentioning that addresses in "source" tables ("time-sample" for "time-profile", "kdebug-counters-with-pmi-sample" for "cpu-profile" and "counters-profile") are correct (or, at least, are correctly aligned aligned). Here's an example: % xctrace version xctrace version 15.2 (15C500b) # run recording % xctrace record --template "Time Profile" --output TP.trace --launch /bin/dd if=/dev/random of=/dev/null bs=1024 count=1048576 # extract "source" table % xctrace export --input TP.trace --xpath='/trace-toc/run[1]/data/table[@schema="time-sample"]' > tp.time-sample.xml # extract "derived" table % xctrace export --input TP.trace --xpath='/trace-toc/run[1]/data/table[@schema="time-profile"]' > tp.time-profile.xml % xmllint --xpath '//row[1]' tp.time-sample.xml <row><sample-time id="1" fmt="00:00.040.502">40502000</sample-time><thread id="2" fmt="Main Thread 0x37c2d0a (dd, pid: 32471)"><tid id="3" fmt="0x37c2d0a">58469642</tid><process id="4" fmt="dd (32471)"><pid id="5" fmt="32471">32471</pid><device-session id="6" fmt="TODO">TODO</device-session></process></thread><core id="7" fmt="CPU 4 (P Core)">4</core><thread-state id="8" fmt="Running">Running</thread-state><sentinel/><kperf-bt id="9" fmt="PC:0x1863149fc, 3 frames, 1 regs, pid: 32471"><text-addresses id="10" fmt="frag 1717">6546645708 6546360308 0</text-addresses><text-address id="11" fmt="0x1863149fc">6546344444</text-address><process ref="4"/><register-content id="12" fmt="0x2e4c00018635e2cc">3336041430521340620</register-content></kperf-bt><time-sample-kind id="13" fmt="Timer Fired">0</time-sample-kind></row> % xmllint --xpath '//row[1]' tp.time-profile.xml <row><sample-time id="1" fmt="00:00.040.502">40502000</sample-time><thread id="2" fmt="Main Thread 0x37c2d0a (dd, pid: 32471)"><tid id="3" fmt="0x37c2d0a">58469642</tid><process id="4" fmt="dd (32471)"><pid id="5" fmt="32471">32471</pid><device-session id="6" fmt="TODO">TODO</device-session></process></thread><process ref="4"/><core id="7" fmt="CPU 4 (P Core)">4</core><thread-state id="8" fmt="Running">Running</thread-state><weight id="9" fmt="1.00 ms">1000000</weight><backtrace id="10"><frame id="11" name="0x1863149fd" addr="0x1863149fd"><binary id="12" name="dyld" UUID="324E4AD9-E01F-3183-B09F-3E20B326643A" arch="arm64e" load-addr="0x186313000" path="/usr/lib/dyld"/></frame><frame id="13" name="0x18635e2cc" addr="0x18635e2cc"><binary ref="12"/></frame><frame id="14" name="start" addr="0x1863187f4"><binary ref="12"/></frame></backtrace></row> As you can see, <kperf-bt id="9" fmt="PC:0x1863149fc, 3 frames, 1 regs, pid: 32471"> refers to a properly aligned address, but the address from <backtrace id="10"><frame id="11" name="0x1863149fd" addr="0x1863149fd">... is off by one. It seems like only an address from the top frame is incorrect, as others are aligned properly. The same issue exists for "CPU Profile" and "CPU Counters" instruments and could be reproduced on macOs running on both x86-64 and Apple-Silicon CPUs.
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479
May ’24
"Swift closure context (unknown layout)" memory leak with SwiftUI
I'm introducing some SwiftUI into a primarily UIKit app and have noticed that, as soon as a SwiftUI view is presented / pushed to the nav stack in its hosting view controller, the memory graph shows a number of Swift closure context (unknown layout) entries under an <unknown> header. These entries persist after the SwiftUI view has been popped from the navigation stack. Is this cause for concern? I don't think it represents a memory leak within my app, because the entries are grouped under <unknown> as opposed to my app name. But I'm not entirely sure why they exist (and crucially, why they persist). It's possible to observe this behaviour with a really simple demo app. Just push the following view: struct ViewController02: View { var body: some View { Text("Hello, world!") } } onto a navigation stack: self.navigationController?.pushViewController(UIHostingController(rootView: ViewController02()), animated: true) Any advice / guidance / reassurance would be much appreciated. There can be a considerable number of these entries but I can't see how I could be causing a retain cycle.
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706
Mar ’24
Tracking domains - Network Instrument Points of Interest
Hello, This relates to NSTrackingDomains for Privacy Manifest. Following doc here https://developer.apple.com/documentation/xcode/detecting-when-your-app-contacts-domains-that-may-be-profiling-users. (Also, I'm quite new to using the Network Instrument). I'm not seeing any "Points of Interest" but I know my app has domains that should be shown as "Faults". Do I need to os_log to my Objective-C codebase. I don't have access to the code of various 3rd party SDKs. The doc mentioned above made it sound like these domains should automagically appear. Thanks!
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897
Mar ’24
How do I see the actual leaked bytes Instruments has identified for me?
I am using the Leaks instrument, and it has identified a bunch of 32 and 48 byte "Malloc" leaks. I would like to see a hex dump of some (or all) of those areas. I think if I can see what is in them I can get a better idea about what is triggering the leak. I'm pretty sure it is a real leak. What is the easy way to do this? Can it be done inside instruments, or do I need to run my app under instruments and also attach via lldb and hexdump from lldb? (can I attach lldb and instruments at the same time?) If it matters I'm debugging an iPadOS app, and it is written in Swift plus ObjC, plus ObjC++, oh, and some straight C++.
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523
Mar ’24
Apply Fixups taking too long during iOS app launch
Hello everyone, Our iOS app is taking too long to launch. On checking the launch profile, we are seeing that most of the launch time is being spent in applying fixups which is taking more than a second and at times even more to complete. Our deployment target is iOS 15+. We have checked using dyld_info that our binary uses chained fixups. Since chained fixups are enabled, page-in linking should also be enabled for our app as per this WWDC session. Can someone please help us understand why the fixups application is taking this long and how can we improve it? Thanks.
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532
Apr ’24
Which instructions are included in the hardware event `INST_SIMD_ALU`?
I asked this on StackOverflow too, but did not get a response. Copying verbatim (images might not work as expected). Short question: which instructions other than floating point arithmetic instructions like fmul, fadd, fdiv etc are counted under the hardware event INST_SIMD_ALU in XCode Instruments? Alternatively, how can I count the number of floating point operations in a program using CPU counters? I want to measure/estimate the FLOPs count of my program and thought that CPU counters might be a good tool for this. The closest hardware event mnemonic that I could find is INST_SIMD_ALU, whose description reads. Retired non-load/store Advanced SIMD and FP unit instructions So, as a sanity check I wrote a tiny Swift code with ostensibly predictable FLOPs count. let iterCount = 1_000_000_000 var x = 3.1415926 let a = 2.3e1 let ainv = 1 / a // avoid inf for _ in 1...iterCount { x *= a x += 1.0 x -= 6.1 x *= ainv } So, I expect there to be around 4 * iterCount = 4e9 FLOPs. But, on running this under CPU Counters with the event INST_SIMD_ALU I get a count of 5e9, 1 extra FLOP per loop iteration than expected. See screenshot below. dumbLoop is the name of the function that I wrapped the code in. Here is the assembly for the loop +0x3c fmul d0, d0, d1 <---------------------------------- +0x40 fadd d0, d0, d2 | +0x44 fmov d4, x10 | +0x48 fadd d0, d0, d4 | +0x4c fmul d0, d0, d3 | +0x50 subs x9, x9, #0x1 | +0x54 b.ne "specialized dumbLoop(_:initialValue:)+0x3c" --- Since it's non-load/store instructions, it shouldn't be counting fmov and b.ne. That leaves subs, which is an integer subtraction instruction used for decrementing the loop counter. So, I ran two more "tests" to see if the one extra count comes from subs. On running it again with CPU Counters with the hardware event INST_INT_ALU, I found a count of one billion, which adds up with the number of loop decrements. Just to be sure, I unrolled the loop by a factor of 4, so that the number of loop decrements becomes 250 million from one billion. let iterCount = 1_000_000_000 var x = 3.1415926 let a = 2.3e1 let ainv = 1 / a // avoid inf let n = Int(iter_count / 4) for _ in 1...n { x *= a x += 1.0 x -= 6.1 x *= ainv x *= a x += 1.0 x -= 6.1 x *= ainv x *= a x += 1.0 x -= 6.1 x *= ainv x *= a x += 1.0 x -= 6.1 x *= ainv } print(x) And it adds up, around 250 million integer ALU instructions, and the total ALU instructions is 4.23 billion, somewhat short of the expected 4.25 billion. So, at the moment if I want to count the FLOPs in my program, one estimate I can use is INST_SIMD_ALU - INST_INT_ALU. But, is this description complete, or are there an other instructions that I might spuriously count as floating point operations? Is there a better way to count the number of FLOPs?
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379
Apr ’24
Regarding network connection blocking of NSPrivacyTrackingDomains
・Xcode 15.1 ・The app is also compatible with Watch. In the privacy manifest, we defined NSPrivacyTracking to YES and NSPrivacyTrackingDomains to specific domains. Furthermore, to avoid warnings when uploading to Testflight, we have implemented a privacy manifest file in the app with the following configuration. ・Place the .xcprivacy files for the app itself and WatchExtension under their respective Target directories. ・Settings related to tracking domains are listed in .xcprivacy of the app itself. ・In .xcprivacy of WatchExtension, only describe the reason for UserDefault of NSPrivacyAccessedAPIType However, these implementations do not block network connections, "Fault" still occurs on "Point of Intereset instruments". Is there something wrong with my implementation?
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429
Apr ’24
Unknown network connection Xcode instruments
Users have reported unusually high data usage with my app. So to investigate I have profiled in instruments. My app as expected in using minimal data. However in instruments I see an "Unknown" process. Which sends around 1mb of data every 2 seconds. Can anyone explain what unknown process is? Sorry my question is vague but I'm at the beginning of understanding the instruments outputs so your help is so very much appreciated.
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404
May ’24
Custom keyboard extension modified to allow full access back to App being killed
Hello, technical friends, I am developing a custom keyboard extension, currently encountered a technical difficulty, almost asked AI and Google have not solved my problem. 

 Problem description: 
 When my App was first installed, I opened Settings from the App, enabled full access, and crashed when I returned to the App. Run the App for the second time, open the Settings from the App, update the full access permission, and automatically re-run the App after returning to the App, and then the third, fourth, and NTH times will not crash. 

 Seems like ios will kill host apps for custom keyboard extensions after full access is updated? I want my App installed for the first time to update full access to return App without crashing, but don't know how to fix this problem. I look forward to the technical experts working in Apple development to help me provide relevant technical methods and ideas so that I can solve this problem. Thank you very much! When tracing debugging in xcode, after the App forces exit, the console prompts: Message from debugger: Terminated due to signal 9 When I was monitoring CPU and memory usage, it was very low and I didn't see anything unusual.
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312
May ’24
how to make shared propery async
I was watching https://developer.apple.com/videos/play/wwdc2023/10248/ , in this video it is adviced to make below shated property async to benefit from concurency (in video 40:04 , exact time) , do yo know how to do it ? class ColorizingService { static let shared = ColorizingService() func colorize(_ grayscaleImage: CGImage) async throws -> CGImage // [...] } struct ImageTile: View { // [...] // implicit @MainActor var body: some View { mainContent .task() { // inherits @MainActor isolation // [...] result = try await ColorizingService.shared.colorize(image) } } }
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268
May ’24