On 06/01/16(Wed) 11:19, Landry Breuil wrote: > [...] > i've had multiple ppl coming to me privately about this - Yes, > performance with firefox has been steadily degrading in the past > releases, since around 39 or so - i'm aware of this, but nobody is > actually working on it - i won't/can't since this is way out my skills > and i have no time nor motivation for that. > > Debugging this requires profiling / running the browser within ktrace > and figuring out why apparently it does way much more syscalls than > before, which might be a clue, or not. Of course since you cant really > use traditional tools like gdb, your toolbox is empty. Or that could be > graphical stack regressions. Or so many other things. The builtin > profiler needs specific code to work on OpenBSD. > > Anybody is welcome to look into it - or 5.9 will ship with firefox 43 > as is.
I started looking at this but didn't go far. It seems that the problem is related to/exposed by the use of pthread_mutex_lock(3) & friends. I tried to analyze ltrace(1) outputs, but I got lost in Firefox's sources. I really don't know where to look at. Here's what I wrote two months ago: On 18/11/15(Wed) 20:44 +0100, Martin Pieuchot wrote: > The actual firefox port (not the -esr one) might be exposing a bug in > librthread resulting in a storm of sched_yield(2) calls when multiples > threads are trying to access the same lock, see _spinlock(). > > I generated two ltrace(1) dumps for librthread hackers to have a look > at. They are both generate with a hacked version of ltrace(1) with: > > $ ltrace -p $pid -t cu -u libpthread ; sleep 2; ktrace -C > > After having started firefox with: > > $ LD_TRACE_PLT="" LD_TRACE_PLTSPEC="libpthread" DISPLAY=:0 firefox > > > The dumps are generate while firefox is sitting in its own custom home > page. > > > kump-esr.txt a dump of the firefox-esr which work "not so bad" > > kdump-nightly.txt a dump of firefox's trunk which expose the problem > > > $ grep sched_yield kdump-esr.txt |wc -l > 4 > $ grep sched_yield kdump-nightly.txt |wc -l > 89418 > > > The sequence below is an extract of what you can find there, when you > have multiple threads fighting for the malloc lock... this goes on > forever and gets even worse when thread 1019109 returns from thrsleep... > > Apparently they are all waiting for thread 1010468 to release the malloc > lock or... is it bad doctor? > > > 13288/1032189 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin USER .plt symbol: 7 bytes "__errno" > 13288/1032189 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin USER .plt symbol: 19 bytes > "_thread_malloc_lock" > 13288/1032189 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin USER .plt symbol: 11 bytes "_spinunlock" > 13288/1010095 firefox-bin USER .plt symbol: 9 bytes "_spinlock" > 13288/1027370 firefox-bin USER .plt symbol: 7 bytes "__errno" > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin USER .plt symbol: 19 bytes > "_thread_malloc_lock" > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1027370 firefox-bin USER .plt symbol: 9 bytes "_spinlock" > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1027370 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin RET sched_yield 0 > 13288/1032189 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1032189 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin RET sched_yield 0 > 13288/1027370 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1027370 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin RET sched_yield 0 > 13288/1032189 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1032189 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1027370 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1027370 firefox-bin CALL sched_yield() > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin RET sched_yield 0 > 13288/1032189 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1032189 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1027370 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1027370 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1032189 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1027370 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1032189 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1027370 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin RET sched_yield 0 > 13288/1010095 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin CALL sched_yield() > 13288/1032189 firefox-bin USER .plt symbol: 12 bytes "_atomic_lock" > 13288/1010095 firefox-bin RET sched_yield 0 > 13288/1032189 firefox-bin CALL sched_yield() > 13288/1027370 firefox-bin RET sched_yield 0 > ...
