obviously i've tested this with 32/33/34 a dozen or so times, but the performance regression shows up in all of them, so i've only copied that particular one. the best (i.e. "least bad for the bugged kernel") result so far was "only" -18%, and most runs are down by 25-30%.
** Package changed: ubuntu => linux (Ubuntu) -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1795116 Title: large performance regression (~20-40%) in wifi with 4.15.0-33 and later Status in linux package in Ubuntu: New Bug description: 16.04 install using the HWE stack. after several weeks of uptime on -32, an update to -34 showed a major drop in wifi throughput, dependent solely on the kernel chosen: $ uname -a && ./wifibench.sh Linux brix 4.15.0-32-generic #35~16.04.1-Ubuntu SMP Fri Aug 10 21:54:34 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux Tue 25-Sep-18 06:07 PlatformSDK-SVR2003R2.iso 429,840,384 100% 8.41MB/s 0:00:48 (xfr#1, to-chk=0/1) sent 429,945,420 bytes received 35 bytes 8,685,766.77 bytes/sec $ uname -a && ./wifibench.sh Linux brix 4.15.0-34-generic #37~16.04.1-Ubuntu SMP Tue Aug 28 10:44:06 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux Tue 25-Sep-18 06:14 PlatformSDK-SVR2003R2.iso 429,840,384 100% 4.83MB/s 0:01:24 (xfr#1, to-chk=0/1) sent 429,945,420 bytes received 35 bytes 5,028,601.81 bytes/sec (the script is a simple rsync from a NAS. nothing in the NAS, or the router, or the physical positions of the devices or etc etc has changed, let alone in those 7 minutes). there is no interference, no other devices connected, etc. prior to the transfer, the link quality is 62-64 and the signal similarly weaker because of power saving, but once packets are in flight it looks perfect: $ iwconfig wlan0 IEEE 802.11 ESSID:"****" Mode:Managed Frequency:2.452 GHz Access Point: **** Bit Rate=150 Mb/s Tx-Power=20 dBm Retry short limit:7 RTS thr=2347 B Fragment thr:off Power Management:on Link Quality=70/70 Signal level=10 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:15 Missed beacon:0 the client is a J1900-based (baytrail) machine with a RTL8723BE wifi module. average performance while on -32 was consistently 70-80 Mb/s, over a period of several weeks. with -33 and later, it's generally 50-65. (that machine has no access to launchpad. i'll try apport-cli over the weekend). To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1795116/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
