Warren Togami wrote:
Will Cohen wrote:
> I work on performance tools at Red Hat. I have been told there is
> interest in tuning the desktop to improve performance. I have a number
> of questions to help identify the work needed in this area. I would be
> interested in any answers that people have for the following questions.
>
On a somewhat related topic of desktop performance, recently fedora.us
Extras has begun experimenting with -Os rather than the standard -O2
optimization for our firefox & thunderbird packages. So far it seems to
be working very well, with noticably smaller binary RPMS and runtime
memory footprint of these two very large applications. I asked gcc
developers if they had a guess about which -O2 and -Os would be "faster"
for large applications like firefox & thunderbird. They generally
replied that they have no idea, because compiler optimization is an
inexact science. All kinds of other factors come into play like smaller
memory footprint (less swapping), smaller code size (maybe better use of
CPU cache).
It is quite possible that the saving in space could give significant
performance benefits. Code fitting better in instruction cache, fewer
page misses, and paging could be a large win than getting some inner
loop to run faster.
Have there been any past discussions about changing the standard
compiler optimization for perhaps FC3?
I have seen some discussions on -Os vs -O2, but I haven't seen actual
performance comparisons.
> What specific performance problems have people observed so far in
the
> desktop? For example heavy CPU or memory usage by particular
> applications. Another example long latency between event and resulting
> action.
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=100423
One long standing desktop bug that has annoyed me personally is
Evolution's extreme performance problems when dealing with a large
amount of mail in dozens of IMAP folders. It literally takes MINUTES
for evolution-1.4.x or evolution-1.5.x to start and read the first
message in any IMAP folder due to this problem, while Mozilla,
Thunderbird and KMail show new mail almost instantly.
(This report also describes an unrelated 100% CPU usage in resizing
panes horizontally.)
Aside from Evolution, I personally see rpm's huge memory footprint as
being a huge problem. Recently I did a full upgrade of FC1 "Everything"
to FC2 in a single rpm transaction on a box with 256MB RAM. It took
almost 7 hours due to a massive amount of swapping as rpm's memory
footprint climbed past 400MB. We really need to improve this situation.
I would ask for optimization of rpm's memory footprint to be a high
priority for FC3 timeframe, but it may be too scary of a problem. =(
Jeff Johnson has mentioned the performance problems with the rpm
internals to me before.
On a somewhat related note, the rhn-applet uses more than 30MB of
virtual memory. That is just WAY too big. Also look at its CPU time
after a few days running. The combined time of it doing *something*
seems a bit too much IMHO.
30 MB? Do you have anymore details on that, e.g. space for code and
data? Where there just a huge number of libraries being pulled in?
Aside from individual applications that need fixing for severe
performance problems like the above examples, I see our current desktop
software has having poor or lacking behavior in the area of application
usage feedback as being a severe usability weakness.
Currently we have somewhat acceptable Application Startup Feedback in
both GNOME and KDE when programs are launched via panel or menu
launchers from .desktop files. The cursor changing to an hour glass or
otherwise showing motion and activity when you launch "mozilla" gives
the user the feeling that "something is happening" and they must wait.
Without application startup feedback, users click on the launcher
several more times, and bad things happen.
Application Startup Feedback is today not perfect in both GNOME and KDE.
It all cases that I am aware of, launching an application from another
(i.e. URL handler in gaim) does not trigger the mouse cursor to show
activity.
This is somewhat related to what I feel is another huge related weakness
in our current desktop software: Application Busy Feedback. Within
applications, users expect feedback from various operations to indicate
that various apps, or parts of apps are busy doing something. Windows
seems to have two levels of "busy" feedback. One with the tiny
hourglass next to the pointer, and another with the entire cursor
turning into an hourglass. I personally see that is quite effective
when applications embrace this type of functionality in a fine-grained way.
I am not a desktop developer, so I don't know much about the technical
guts under the things I described here. Any explanation, links to
specifications, and mention of future development related to Application
Feedback would be appreciated.
Response time for actions has come up in a number of the responses to my
mail. If the response was very fast, then the feedback wouldn't be an
issue. However, given the response times, it appears that the system
isn't reacting to the input.
Some developers have used strategic printf and accesses to get data out
like how long it took to get from here to there. Another thing we might
consider is the ability to start and stop oprofile sampling at
particular places in code. For example, instrument the code to start
oprofile sampling on a particular action and then stop oprofile sampling
on another event. This would avoid interesting data getting buried in
the long term data. Using oprofile in this manner would give a better
picture of what sections of code are getting exercised for certain actions.
-Will