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

[Christoph Cullmann (cullmann.io)]

On 2022-06-19 21:10, Milian Wolff wrote:
> 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

Hi,

from top of my head what could be an issue is that we do use stuff like

QtConcurrent::blockingMap

inside runnables.

We have one runnable per project, we have one thread pool for them.

But I would assume the QtConcurrent again will span as many threads
as cores per default.

That might lead to suboptimal performance.

But I could be wrong.

Greetings
Christoph

-- 
Ignorance is bliss...
https://cullmann.io | https://kate-editor.org