Christian Hergert wrote:
For those not familiar with Sysprof, or profiling the desktop at
large,
generally a single program is not the problem. The performance problems
often exist across a number of processes.
[…]
The most used collector, however, is the perf collector which is
just
reading from a perf fd mmap'd into a ring buffer.
So it looks like what you folks are doing is actually very similar to what
Facebook is doing. That is interesting, and explains why some GNOME
developers are jumping on the bandwagon of this Change proposal.
The perf collector doesn't record the whole stack because the
amount of
time it takes to decode a 30 second system-wide capture with DWARF/etc is
so slow practically nobody would use it.
So this is basically the same issue that Facebook is having.
Could we write a new data collection module that does DWARF unwinding
and
stashes some 8kb of stack? Sure. Would people use it? Probably not,
because again, it's so slow that people will start profiling by intuition
again which is probably the worst of all options.
Does profiling individual applications file under "profiling by intuition"
for you? Because that is what I would expect developers to go back to if
systemwide profiling stops being viable.
To my knowledge, we don't have this tooling anywhere else on
Fedora. The
sad part is, those who want to casually drive by and fix performance start
with "recompile the stack with jhbuild" or I guess RPMs/koji if you're
into that sort of thing.
And is it such a problem to require the handful developers who need to do
systemwide profiling to do that, instead of slowing down the production
installation for all users?
Kevin Kofler