$ strace iceweasel 2>&1 | tee /tmp/iceweasel.log

$ cut -d "(" -f 1 /tmp/iceweasel.log | sort | uniq -c | sort -h | tail
   4703 madvise
   9848 mprotect
  12192 write
  12370 read
  12828 writev
  33242 futex
  70842 recvmsg
  72170 poll
  75526 gettimeofday
 477786 clock_gettime

i'm guessing it doesn't need to check the clock that many times :P

the lines are mostly like this:

clock_gettime(CLOCK_MONOTONIC, {tv_sec=315404, tv_nsec=808093294}) = 0

i forgot to mention that when this happens tabs can't load any pages

My first suspicion would be misbehaving JS on one of the 15 tabs.

Can you take a look at:

about:preformance

about:memory

Next suspicion would ba an out of date extension or plug-in

can you reproduce this with addons disabled?

i was going to, but the problem was that nothing changed except for the upgrade, otherwise i wouldn't have reported it. anyway it's not happening today after several hours :/

i could not reproduce this on x86_64 - i watched the CPU closely
while the browser started for the first time, and loaded a few
tabs - im guessing this was something an add-on was doing

i started `iceweasel --safe-mode` and the high cpu was there again after a while, closing tabs doesn't stop it :/

Hmmm.. wanted to play along..

did: pacman -Sy iceweasel (because my system is busy so didn't want the full upgrade right now.

Loaded a bunch of tabs. Wrote this, Scrolled kitten feeds, watched cat videos.

CPU still at under 5%

I'll wait longer.. bit there must be something I'm doing different.

loaded more tabs, watched more vids, Still not seeing CPU creep, I'll keep waiting

could you run `strace iceweasel 2>&1 | tee /tmp/iceweasel.log` and check if the `clock_gettime` has something to do with this?

well, it keeps happening even in safe mode, i closed all tabs and even went to about:serviceworkers and unregistered everything -- cpu's still 140% and starts after a while with no manual action, i just left it open

I'll try the strace tomorrow when I have more time... this is form the same iceweasel as above... still less then 5% CPU usage..

Theres gotta be something different about my set-up I guess.

oops just realized that mine is running in a firejail so that could be a big part of the difference...

Let me launch one outside of the jail....

k, not in a firejail now but so fat the CPU usage still looks flat.. I'll let it cook for a bit more to be extra sure.

welll... lotsa scrolling, lotsa back and forth between the way too many tabs, videos watches, etc, etc,etc.

Still flat CPU usage. Will do the strace of a non-firejailed iceweasel first thing tomorrow.

running the same command you did on the strace produces:

   2776 stat
   3798 getpid
   5592 madvise
   6344 mprotect
  27153 write
  31585 read
  84106 writev
 133503 futex
 348895 poll
 363860 recvmsg

i did this with about 6 tabs running, one of them in a private
browsing session, and i played 30 minute video, with pulseaudio
running

   1427 mmap
   6204 madvise
   7266 stat
  15527 mprotect
  24154 write
  27861 writev
  99537 futex
 143584 read
 664083 poll
 784381 recvmsg

great, thanks! i remembered i changed some things in about:config a few days before upgrading so i undid them, but it happened again. then i made a new profile and even synced everything through firefox sync and both profiles have been working ok since this morning :/