Slow startup, possibly due to too many calls to getpid()

[misev]

Describe the bug
kitty takes ~0.6s to start on my machine which is perceptibly quite slow.
I ran it with strace which showed that most of the time is spent in a lot of (~80,000) calls to getpid()

293934 1591634753.176957 brk(0x202d000) = 0x202d000 <0.000010>
293934 1591634753.182584 brk(0x204e000) = 0x204e000 <0.000012>
293934 1591634753.185616 getpid()       = 293934 <0.000008>
293934 1591634753.185649 getpid()       = 293934 <0.000006>
293934 1591634753.185679 getpid()       = 293934 <0.000006>
293934 1591634753.185715 getpid()       = 293934 <0.000006>
293934 1591634753.185741 getpid()       = 293934 <0.000005>
293934 1591634753.185769 getpid()       = 293934 <0.000004>
...
293934 1591634754.457158 getpid()       = 293934 <0.000003>
293934 1591634754.457171 getpid()       = 293934 <0.000003>
293934 1591634754.457184 getpid()       = 293934 <0.000003>
293934 1591634754.457197 getpid()       = 293934 <0.000003>
293934 1591634754.457210 getpid()       = 293934 <0.000003>
293934 1591634754.457223 getpid()       = 293934 <0.000003>
293934 1591634754.457236 getpid()       = 293934 <0.000003>

You can check with strace -f -ttt -T -o strace-analysis.txt kitty

Expected behavior
The startup is perceptibly slow, I'd expect it to be faster. The --single-instance option makes no difference.

Enviroment details
OS: Kubuntu 20.04

kitty 0.17.4 (3d32202b3a) created by Kovid Goyal
Linux hifi 5.4.0-33-generic #37-Ubuntu SMP Thu May 21 12:53:59 UTC 2020 x86_64
Ubuntu 20.04 LTS \n \l
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION="Ubuntu 20.04 LTS"
Loaded config files: /etc/xdg/kitty/kitty.conf, /home/dimitar/.config/kitty/kitty.conf
Running under: X11

Config options different from defaults:
active_tab_title_template  {title}
allow_remote_control       y
background                 Color(red=28, green=40, blue=54)
bold_font                  Iosevka Term Heavy
bold_italic_font           Iosevka Term Heavy Italic
color1                     Color(red=249, green=85, blue=95)
color10                    Color(red=52, green=187, blue=153)
color11                    Color(red=255, green=255, blue=85)
color12                    Color(red=88, green=156, blue=245)
color13                    Color(red=231, green=85, blue=152)
color14                    Color(red=57, green=120, blue=187)
color2                     Color(red=32, green=175, blue=137)
color3                     Color(red=253, green=240, blue=41)
color4                     Color(red=88, green=156, blue=245)
color5                     Color(red=147, green=77, blue=149)
color6                     Color(red=30, green=158, blue=230)
color7                     Color(red=187, green=187, blue=187)
color8                     Color(red=84, green=84, blue=84)
color9                     Color(red=250, green=139, blue=142)
cursor                     Color(red=187, green=187, blue=187)
enable_audio_bell          False
font_family                Iosevka Term Medium
font_size                  12.0
foreground                 Color(red=255, green=255, blue=255)
italic_font                Iosevka Term Medium Italic
repaint_delay              16
scrollback_lines           50000
select_by_word_characters  :@-./_~?&=%+#
selection_background       Color(red=180, green=213, blue=255)
selection_foreground       Color(red=28, green=40, blue=54)
single_window_margin_width FloatEdges(left=-1000.0, top=-1000.0, right=-1000.0, bottom=-1000.0)
strip_trailing_spaces      smart
tab_bar_edge               1
window_margin_width        FloatEdges(left=1.0, top=1.0, right=1.0, bottom=1.0)
Added shortcuts:
	control+page_up KeyAction(func='previous_tab', args=())
	control+page_down KeyAction(func='previous_tab', args=())
Changed shortcuts:
	shift+control+w KeyAction(func='close_tab', args=())

Additional context
kitty --config NONE doesn't change the startup time.

[kovidgoyal]

kitty doesnt have any calls to getpid() at all, grep the codebase for it
and you will see exactly 4 instances, exactly one of which is called
during normal startup exactly once. I have no idea where the getpids are
coming from but it isnt kitty code. And while I do see the large number of
getpids() in my strace too, so it would be interesting to track them
down, they dont cause a slowdown for me.

time kitty false

real 0.344
user 0.241
sys 0.076
maxmem 80 MB
faults 0

And with single instance it is instantaneous, for all calls after teh
first

time kitty -1

real 0.097
user 0.086
sys 0.010
maxmem 21 MB
faults 0

[kovidgoyal]

For the getpids() they are happening somewhere in the course of
create_os_window() in glfw.c

[kovidgoyal]

And further they come from glfwCreateWindow

[kovidgoyal]

And as far as I can tell the getpids come from glXGetFBConfigAttrib()
which is a LGX library function. Nothing kitty can do about this as far
as I can see. It would be nice if GLX provided an API to get fraebuffer
config attribs in bulk but as far as I can tell it doesnt.

[kovidgoyal]

One possible mitigation would be to cache the results of
chooseGLXFBConfig, that would reduce the number of getpids() to a
quarter

[misev]

Right, it was most plausible that the getpids are likely from some library and not kitty itself. Great that you found a way to reduce them, I'm curious if it in turn reduces the startup time.
The original startup time I reported was on an older machine from 2012, now testing on a recent one I get a similar timing of 0.33s.

[kovidgoyal]

On my machine startup time was reduced by abt 25%

[kovidgoyal]

And by using an API from GLX 1.3 I have the number of getpids() down to
the hunreds.

[misev]

Great, I just tried master and can confirm it's ~25% faster!