On Tue, Jun 24, 2025 at 11:08 AM Davide Cavalca <dcava...@fedoraproject.org> wrote: > > 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. >
+1, I'd start with omitting leaf frame pointers only in glibc, if we absolutely must. Unfortunately I'm not a compiler hacker, so I can't really address -mno-omit-leaf-frame-pointer not working (at least in some situations). But in general, do you notice a measurable effect from removing -mno-omit-leaf-frame-pointer performance-wise? Or is there any other associated downside to leaving it on, even if it might not kick in in some leaf functions? In our (Meta) production, we have both -fno-omit-frame-pointer and -mno-omit-leaf-frame-pointer, and I haven't seen any particular complaints around that. So unless there is a really good reason to drop leaf stuff, I'd keep it, of course. > Cheers > Davide -- _______________________________________________ devel mailing list -- devel@lists.fedoraproject.org To unsubscribe send an email to devel-le...@lists.fedoraproject.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
