accumulating projects in kate lead to excessive kate startup time due to git

[Milian Wolff]

On Samstag, 18. Juni 2022 14:15:42 CEST Milian Wolff wrote:
> Hey all,
> 
> Kate took ~4s to show its main window on my beefy workstation with lots of
> RAM, CPUs and speedy NVME disks. I found this quite odd and wondered about
> the reason so I sat down and profiled it. Perf shows a lot of external git
> processes running sequentially, which I could also replicate with strace:

<snip>

> b) Can we query the git status in parallel for all projects, instead of
> serially? My machine has 12 cores and 24 threads, and the NVME disk and ram
> should also allow this.

Sorry, hit sent too early...

You can download the perfparser file here:

https://milianw.de/files/kate.slow.startup.perfparser

You can open that in hotspot and then go to the off-CPU time flame graph. 
Basically all of that comes from _really_ slow memory allocations, which is a 
first for me. It seems like my system is suffering from some extreme slowdowns 
in `int_malloc` - but only in kate. Other applications don't show this 
behavior, and I'm unsure where this comes from... See the excessively slow 
calls to rwsem_down_read_slowpath from _int_malloc, even in the main thread. 
If you look at the main thread e.g. there we see ~1s off cpu time from 
_int_realloc by _FcConfigParse::FcStrBufData alone!

I'll try to continue to figure this out
-- 
Milian Wolff
mail at milianw.de
http://milianw.de