On Mon, 2023-02-27 at 18:23 +0100, Florian Weimer wrote: > # Goals > > The purpose of this SIG is to quantify the potential benefits of > applying existing compiler technology to distribution packages, > targeting more recent CPUs, and evaluating different options for how > these optimizations can be maintained in a scalable way, and > delivered > to end users. Would this work fit under the charter of the existing (and largely dormant) Alternative Architectures SIG? > Today, there is a significant delay between the release of new x86-64 > ISAs and the adoption across the entire CentOS distribution. For > example, CentOS 9 Stream released with the x86-64-v2 ISA baseline, > nine > to thirteen years after such CPUs became commercially available. The > concern is that this discrepancy leaves more recent CPU features > unused, > and end users do not see the best possible performance for the CPUs > they > use. > > Parts of the distribution are built with run-time selected > optimizations, but this only applies to specialized functional areas, > such as string manipulation, certain mathematical operations, and > cryptography, but not (for example) to language interpreters that are > part of CentOS. > > # Status > > Proposed: RFC and looking for a sponsoring Governing Board member > > # What’s in scope > > * Explore the immediate runtime performance impact of package- > specific > ISA-related work on key workloads e.g. language interpreters. > > * Evaluate the performance benefit at run-time of building CentOS > with > auto-vectorization and the very-cheap cost model and different x86- > 64 > micro-architecture levels. > > * Explore ways how these performance-enhancing builds can be > maintained > at the distribution level and made available to end users for > installation. > > * Assess the image/container size impact of those additional > optimized > builds (this may not be applicable to some delivery mechanisms). > > * Explore ways to alert users that they do not get optimal > performance > because of misconfigured hypervisors. > > * It is possible, but not likely, that work across the entire > distribution may be needed to enable shadow stacks. (Userspace > enablement happened as part of CentOS 8, but the kernel parts are > not > upstream and have changed significantly, so there is some > uncertainty.) If large-scale work affecting many packages is > needed, > the SIG would be a natural place to prototype changes before > integration into the distribution. > > # What's not in scope > > * Enablement for future x86 CPUs and chipsets, assemblers, linkers, > and > compiler support for new ISAs including regular performance work on > individual packages (e.g., identified upstream backports). Hardware > enablement must follow existing processes. > > * Any 32-bit work (such as 64-bit time_t, or a 32-bit kernel) is > explicitly excluded. > > * The focus will be on userspace changes. > > * Rebuilds for potential observability improvements are out of scope > (although shadow stacks are expected to help in this a > > * Adding additional hosts to the CentOS infrastructure in support of > this SIG needs to be negotiated with the CentOS infrastructure > team. The CPU microarchitecture level of the existing > infrastructure > is already sufficient. > > # Roadmap > > March 2023: Start the SIG and coordinate with partners > April 2023: Adopt existing CentOS builder resources to deliver the > required builds. > May 2023: Initial performance analysis results. > > Rest TBD based on results of exploration. > > Resources > > They SIG could benefit from spare x86-64 Koji builder capacity. > > _______________________________________________ > CentOS-devel mailing list > CentOS-devel at centos.org > https://lists.centos.org/mailman/listinfo/centos-devel