On Thu, Nov 27, 2014 at 6:54 PM, PCMan <pcman...@gmail.com> wrote:
> More on this topic. I also did benchmarks using strace.
> First, I dropped all caches by doing echo 3 > /proc/sys/vm/drop_caches.
> Then I used strace to trace all of the child processes of sddm, and then
> login.
> This is the result I got.
>
> https://drive.google.com/file/d/0B4BhmC8V2mivMGFRS3BCeFk0ZTQ/view?usp=sharing
>
> We have more than 600,000 system calls during LXQt startup.
> This is pretty amazing. More than half of them are just "stat" calls used to
> locate icons in the icon theme. This is caused by QIcon::fromTheme() (or the
> fixed version in libqtxdg).
> Unfortunately, this inefficient poor design is actually "correct" according
> to the xdg icon theme spec. Gtk+ solves this with an optional icon cahce. I
> believed that KDE does this, too.
> To reduce unnecessary I/O, we definitely need some icon theme cache
> mechanisms.
> However, I'm not sure how much benefit can this brings. It does not seem to
> be the major cause of slow startup.
> The impact of relocations caused by huge C++ libraries and ld.so is more
> prominent than these system calls.
> Hence, I think it might be a good idea to use the same hack as kdeinit
> (pre-link, fork, and load modules) to speed up.
> To do this, we need to make main desktop components loadable modules.
> Comments are welcomed.
The C++ rellocations have probably the highest impact during the startup.
Just by using pre-link my startup time, on a weak machine, was roughly
reduced to half. Other improvements should aldo be deployed, but
pre-link comes at the top of the list.
I'm working on inproving libqtxdg XdgDesktopFile loading and
XdgDesktopFileCache performance.
--
Luís Pereira
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