so, the methodology is, reboot, wait for things to settle (i.e. for the
initial "performance" cpu period ubuntu uses to pass), run a simple
script that dumps out some diags and rsyncs that 400MB iso.
--
Linux brix 4.19.0-041900rc6-generic #201809301631 SMP Sun Sep 30 16:32:51 UTC
2018 x86_64 x86_64 x86_64 GNU/Linux
Current Frequency:2.452 GHz (Channel 9)
Link Quality=62/70 Signal level=-48 dBm
Wed 03-Oct-18 01:35
429,840,384 100% 6.80MB/s 0:01:00 (xfr#1, to-chk=0/1)
sent 429,945,420 bytes received 35 bytes 7,106,536.45 bytes/sec
---
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
Current Frequency:2.452 GHz (Channel 9)
Link Quality=62/70 Signal level=-48 dBm
Wed 03-Oct-18 01:40
429,840,384 100% 6.38MB/s 0:01:04 (xfr#1, to-chk=0/1)
sent 429,945,420 bytes received 35 bytes 6,665,821.01 bytes/sec
---
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
Current Frequency:2.452 GHz (Channel 9)
Link Quality=70/70 Signal level=-32 dBm
Wed 03-Oct-18 01:43
429,840,384 100% 8.14MB/s 0:00:50 (xfr#1, to-chk=0/1)
sent 429,945,420 bytes received 35 bytes 8,348,455.44 bytes/sec
--
that was the best run 4.19 had, at -18%, out of about a dozen. as with
4.15.0-33 and later most were down by 25-30%. so, "still exists" it is.
here's where things get weird though...
---
Linux brix 4.19.0-041900rc6-generic #201809301631 SMP Sun Sep 30 16:32:51 UTC
2018 x86_64 x86_64 x86_64 GNU/Linux
Current Frequency:2.447 GHz (Channel 8)
Link Quality=66/70 Signal level=-44 dBm
Wed 03-Oct-18 01:12
429,840,384 100% 8.07MB/s 0:00:50 (xfr#1, to-chk=0/1)
sent 429,945,420 bytes received 35 bytes 8,348,455.44 bytes/sec
---
on channel 8(+4), 4.19 typically performed on par with -32 and older.
on channel 9(+5) though it consistently showed the same regression as -33.
again, this is over about a dozen runs (and multiple reboots switching between
kernels), not a onetime event.
-32 though consistently performed at 70+Mb/s averages regardless of channel.
i'm way out of my depth at this point, but that seemed a remarkable
weirdness and worth pointing out. :)
** Tags added: kernel-bug-exists-upstream
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1795116
Title:
large performance regression (~20-40%) in wifi with 4.15.0-33 and
later
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