On 2025-06-24 12:06, Florian Weimer wrote:
Sorry, I tried to make clear that this is regular C code compiled with
the -mno-omit-leaf-frame-pointer flag, like the rest of the
distribution.

The only way in which glibc is special is that Wilco Dijkstra from Arm
has recently optimized malloc to make the happy paths as fast as
possible, intentionally triggering the shrink-wrapping optimization
through careful use of tail-calls to no-inline functions.  Any other
packages can do the same, either manually or even automatically in some
cases, with profile-guided optimization.

I think even before these malloc changes, typical workloads had like 10%
of their profiling samples in code regions where the frame pointer was
not yet set up.  And dropping -mno-omit-leaf-frame-pointer might not
even increase that percentage because short functions without memory
accesses are more likely to drop from profiles altogether.

I agree that based on these findings it can make sense to drop -mno-omit-leaf-frame-pointer for glibc, but I don't this it justifies dropping it distro-wide, at least not without further testing and collecting data on the potential impact.

Cheers
Davide
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