On 18-08-19 13:33, Gordan Bobic wrote:
On Sun, Aug 11, 2019 at 10:36 AM <mcatanzaro(a)gnome.org <http://gnome.org/>> 
 > This seems like a distraction from the real goal here, which is to
 > ensure Fedora remains responsive under heavy memory pressure,

I think this is an overwhelmingly important point, and as somebody regularly 
working with ARM machines with tiny amounts of RAM, it is of considerable 
interest to me.
I typically use CentOS because stability is important to me, but most 
worthwhile things filter to there, so I hope what I'm about to say is not _too_ 

1) Compile options
 From what I can tell from rpm macro options, default on C7 seems to be -O2. 
-Os seems to help in most cases.

I don't think it is likely that Fedora will switch to -Os

Adding -ffunction-sections -fdata-sections to defaults can help considerably in 
producing smaller binaries, and is not the default.
Linking with -Wl,--gc-sections helps a lot and is not the default

These OTOH are interesting I know that e.g. uboot combines these and it helps a 
lot to get smaller binaries,
and this should help with RAM size too, since if a page of a binary contains 
mostly unused things and 1 symbol
which is actually used it will still get paged in.

Can you perhaps start a new devel list thread about just this ? Maybe with some 
binary size numbers for
some apps / libs build with and without these options?

Extensive stripping seems to already be the default (--strip-unneeded, removal 
of .comment and .note sections)

2) Runtime condiguration
Default stack size is 8192 (ulimit -s). This unnecessarily eats a considerably 
amount of memory. I have yet to see anything that actually experiences problems 
with 1M.

Actually ulimit -s is the *maximum* stack size, I'm pretty sure the stack will 
start much smaller and
grow dynamically. So changing this is not saving any RAM and it will makes apps 
which do have high
stack usage crash when they hit the new lower limit.


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