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Re: [PATCH] Add ifunc memcpy and memmove for aarch64
On Thursday 09 February 2017 05:10 PM, Szabolcs Nagy wrote:
> ok, it is probably not worth worrying about
> (should be around 0.1% of the minimal startup time now)
>
> but doing it just to control ifunc selection is still
> useful (at least for development)
A simple tunable that disables CPU selection would be nice:
glibc.tune.cpu = default|thunderx|a57
However then you would have to think harder about positioning the cpu
structure initialization in static binaries to have them be controlled
by tunables and not just blindly put them right at the top of
__libc_start as the easy way out. It is something that should be done
anyway.
However, couldn't we do that as an add-on to this patch? I'd really
like this framework to go in early and be exercised a bit because I am
interested in pushing (in the coming weeks hopefully) some optimal
string routines for aarch64.
> (if eventually there will be widespread use of ifunc
> based function multi-versioning then the trap will
> not be per process startup but per module load which
> is a bit more relevant, but also not something we can
> control from the libc)
Right we cannot control that.
Siddhesh