> 2019. 10. 19. 오전 9:17, Alex Zavatone via Cocoa-dev > <cocoa-dev@lists.apple.com> 작성: > > Wow was this ever fun. > > Woo hoo! > > Let this be an exercise in the dangers of memory leaks. > > Our team uses VIPER with everything being strongly linked. Also in > Objective-C, there are cases where private instance variables are used, not > the wrapping properties, not to mention strongly referenced delegates. Who > needs memory management, right? Well, guess what? When you do this, it's > really easy to leak lots of objects and this means lots of mach ports are > requested from Xcode and this means that there are lots of mach ports > requested by the WindowServer and this means that the GPU driver, (SkyLight) > requests more mach ports - until the system says, "no, you can not have any > more.” That happens around 260,000+ mach ports in the WindowServer. This > restarts the GPU. And when the GPU restarts, the system either restarts the > Mac or crashes the user session out to the login screen. > > After a night fixing memory bugs until midnight, I ran our 280 KIF tests and > no more than 20,000 mach ports were requested. And the full test ran all the > way through without rebooting the Mac or crashing out to the login screen. > > Memory leaks matter! > > Oh, and if anyone wants video of watching the Mac reboot when the > WindowServer has over 260,000 mach ports allocated, I'll happily post a link.
Just for curiosity: I would like the link :-) > Cheers, > > Alex Zavatone > >> On Oct 17, 2019, at 12:07 PM, Alex Zavatone via Cocoa-dev >> <cocoa-dev@lists.apple.com> wrote: >> >> As a background, I mentioned that we occasionally have these scary crashes >> while running our iOS tests that either reboot your Mac or crash the user >> process out to the login screen. >> >> Yesterday, I noticed that I could not run our tests at all without crashing >> around a certain area and on 3 different Macs, all with 24 GB or more of RAM. >> >> My speculation that it, might be related to mach ports was entirely correct >> as after 8 crashes, some debug logs finally appeared - but not all the time. >> >> Our iOS UI tests are run by KIF which uses XCTest as its foundation. When >> running these 280+ UI automation scripts in the Simulator, the amount of >> ports used by Xcode increased rapidly as the tests ran for 30 mins and the >> WindowServer process appeared to have about 20,000 more Mach ports allocated >> than Xcode over that time. >> >> Right before the crash happened, the WindowServer had allocated over 256,000 >> ports and Xcode was just behind by a few thousand. Then, all operation >> pauses for a few seconds, the displays go black, and a few seconds later, >> the user login screen appears as the previous user session crashed out. >> >> What happened is that Xcode asked for more ports and asked the WindowServer >> to allocate more ports and the WindowServer asked the GPU driver for more >> ports and thread com.apple.SkyLight.mtl_submit to crash with either a SIGSEV >> or SIGILL. Either the WindowServer or the Skylight framework for >> MetalDevice and caused a GPU restart. The OS then crashed the user session >> out to the login screen. >> >> Now, the question. Why the hell is XCTest causing Xcode to request so many >> Mach ports and never release them until the app is quit or the system >> crashes? >> >> I tested this last night outside of our app with XCTest and KIF simply going >> back and forth between two screens in an iOS app several thousand times In >> the Simulator. The mach ports of both Xcode and the WindowServer go up and >> are not released until the app quits, but not nearly as fast as in our >> tests. >> Is this a mach port leak in XCTest? >> >> Does anyone know the details on the guts of this? >> >> Thanks a lot and I hope this helps someone else. >> >> Alex Zavatone >> >> Sent from my iThing. >> _______________________________________________ >> >> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) >> >> Please do not post admin requests or moderator comments to the list. >> Contact the moderators at cocoa-dev-admins(at)lists.apple.com >> >> Help/Unsubscribe/Update your Subscription: >> https://lists.apple.com/mailman/options/cocoa-dev/zav%40mac.com >> >> This email sent to z...@mac.com > > _______________________________________________ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/cocoa-dev/pcr910303%40icloud.com > > This email sent to pcr910...@icloud.com _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
