Re: ld.so - text and .data application segments to huge pages

[Florian Weimer <fweimer@redhat.com>]

* Daniel Black:

> Hi,
>
> I received this exceptionally large (slightly convoluted) patch to
> MariaDB to move the .text and .data sections to huge pages in the
> MariaDB issue https://jira.mariadb.org/browse/MDEV-24051.
>
> The author Dmitriy Philimonov (Huawei) claimed great gains of "9% in
> TPS speedup. iTLB && dTLB misses reduced in 38 times and 5 times
> respectively. Latency becomes lower, the jitter in the TPS reduced
> significantly", so it's definitely beneficial.
>
> Obviously maintaining such a large loader work around in a userspace
> application is going to be a burden on the skill set of developers we
> have available.
>
> How complex would it be for the glibc elf loader to use huge pages for
> data segments on load? (extending _dl_map_segments with an environment
> variable control like LD_HUGEPAGES I assume).
>
> Is there any required kernel work to implement this feature?
>
> Would such a concept be supported by the developer community here?
>
> If so I'm happy to write up a feature request (https://sourceware.org/bugzilla).
>
> Anyone off hand interested in writing it?

I think the kernel already supports this via transparent hugepages, if
you increase the segment alignment via those link editor flags (as in
the proposed patch).

Cc:ing Andrea for additional comments.

Thanks,
Florian
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