Finally i find a temporary solution!rename the file com.apple.nsurlsessiond(Dont delete) in/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/System/Library/UserEventPlugins/com.apple.nsurlsessiond.plugin/to something -com.apple.nsurlsessiondand also the file nsurlsessiond(Dont delete) in/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/libexec/to something -nsurlsessiond

Here is some more logs% sudo lsof | grep nsurlsessiondPassword:UserEvent 60 root txt REG 1,4 30016 1152921500312497946 /System/Library/UserEventPlugins/com.apple.nsurlsessiond.plugin/Contents/MacOS/com.apple.nsurlsessiondnsurlsess 215 _nsurlsessiond cwd DIR 1,4 736 2 /nsurlsess 215 _nsurlsessiond txt REG 1,4 614448 1152921500312495196 /usr/libexec/nsurlsessiondnsurlsess 215 _nsurlsessiond txt REG 1,4 28180 23592776 /Library/Preferences/Logging/.plist-cache.99GYDmPSnsurlsess 215 _nsurlsessiond txt REG 1,4 29062064 1152921500312497147 /usr/share/icu/icudt64l.datnsurlsess 215 _nsurlsessiond txt REG 1,4 10833920 23596379 /private/var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/0/com.apple.LaunchServices.dv/com.apple.LaunchServices-1080-v2.csstorensurlsess 215 _nsurlsessiond txt REG 1,4 1558064 1152921500312496184 /usr/lib/dyldnsurlsess 215 _nsurlsessiond 0r CHR 3,2 0t0 310 /dev/nullnsurlsess 215 _nsurlsessiond 1u CHR 3,2 0t0 310 /dev/nullnsurlsess 215 _nsurlsessiond 2u CHR 3,2 0t0 310 /dev/nullnsurlsess 215 _nsurlsessiond 3 NPOLICY nsurlsess 215 _nsurlsessiond 5u systm 0x1ebb302b93b87b91 0t0 [ctl com.apple.netsrc id 7 unit 7]UserEvent 311 xxxx txt REG 1,4 30016 1152921500312497946 /System/Library/UserEventPlugins/com.apple.nsurlsessiond.plugin/Contents/MacOS/com.apple.nsurlsessiondnsurlsess 345 xxxx txt REG 1,4 614448 1152921500312495196 /usr/libexec/nsurlsessiondUserEvent 8964 xxxx txt REG 1,4 29984 23127670 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/System/Library/UserEventPlugins/com.apple.nsurlsessiond.plugin/com.apple.nsurlsessiondnsurlsess 9001 xxxx txt REG 1,4 761744 23119545 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/libexec/nsurlsessiondcom.apple 9044 xxxx 3w REG 1,4 13597149 23603623 /Users/xxxx/Library/Developer/CoreSimulator/Devices/F0685A70-DEB9-4786-8368-CF98BAC7FD1A/data/Library/Caches/com.apple.nsurlsessiond/Downloads/com.apple.mobileassetd/CFNetworkDownload_O3Y86b.tmp/AssetData/adatxxxx@xxxx-iMac ~ %

I too have this problem,nsurlsessiond downloads about 450MB!this is nsurlsessiond logcwd/txt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/sbin/launchd_simtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/dyld_simtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/libSystem.B.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/libobjc.A.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libcache.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libcommonCrypto.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libcompiler_rt.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libcopyfile.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libcorecrypto.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libdispatch.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libdyld.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/liblaunch.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libmacho.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libremovefile.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_asl.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_blocks.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_c.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_configuration.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_containermanager.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_coreservices.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_darwin.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_dnssd.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_featureflags.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_info.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_m.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_malloc.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_notify.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_sandbox.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_sim_kernel.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_sim_platform.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_sim_pthread.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_trace.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libunwind.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libxpc.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_sim_pthread_host.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_sim_platform_host.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/system/libsystem_sim_kernel_host.dylibtxt/usr/lib/system/libsystem_kernel.dylibtxt/usr/lib/system/libsystem_platform.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/libc++abi.dylibtxt/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/libc++.1.dylibtxt/usr/lib/system/libsystem_pthread.dylibtxt/usr/lib/dyld0/dev/null1/dev/null2/private/tmp/com.apple.CoreSimulator.SimDevice.34D7CA2A-2595-4E6F-9622-2252E0BB5A08/launchd.log3[ctl com.apple.netsrc id 8 unit 38]4->0xe277ad83b83d2d295/tmp/com.apple.CoreSimulator.SimDevice.34D7CA2A-2595-4E6F-9622-2252E0BB5A08/syslogsock6/private/tmp/com.apple.CoreSimulator.SimDevice.34D7CA2A-2595-4E6F-9622-2252E0BB5A08/launches.2019-12-10.20.17.19.log7/private/tmp/com.apple.launchd.ylqXwtBNy6/com.apple.webinspectord_sim.socket8/private/tmp/com.apple.launchd.ylqXwtBNy6/com.apple.webinspectord_sim.socket9/private/tmp/com.apple.launchd.5cVa6VutSZ/Listeners10/private/tmp/com.apple.launchd.26mpQitX06/com.apple.testmanagerd.unix-domain.socket11/private/tmp/com.apple.launchd.5cVa6VutSZ/Listeners12/private/tmp/com.apple.launchd.GjbwCBAvpU/com.apple.testmanagerd.remote-automation.unix-domain.socket13/private/tmp/com.apple.launchd.26mpQitX06/com.apple.testmanagerd.unix-domain.socket14/dev/null15/private/tmp/com.apple.launchd.GjbwCBAvpU/com.apple.testmanagerd.remote-automation.unix-domain.socket1617/dev/null