Evaluation report for Emulated Builds

Signed-off-by: Ritesh Raj Sarraf <ritesh.sarraf@collabora.com>

content/designs/x86-build-infrastructure.md

@@ -252,3 +252,49 @@ by modifying the failing packages to make them buildable with a real cross-compi
 This solution requires a much higher maintenance cost as packages do not
 generally support being built in that way, but it may be an option to be able to
 do full builds on x86-64 in the few cases where emulation fails.
+
+## Evaluation Report
+
+A full archive-wide build was run on the Azure Cloud setup, using `x86-64` virtual machines.
+A cloud optimized setup was built, comprising of the following major components:
+
+* Azure provided Linux Virtual Machines (Debian Buster)
+* Docker (as provided by the Linux distribution vendor)
+* Linux 4.19 and above
+* binfmt-support
+* QEMU Emulator
+
+
+Given the task at hand, to run emulation for `ARM` architecture on `x86-64`, we chose
+the following cloud hardware class for our OBS worker setup.
+
+* OBS-Server VM: Standard DS14 v2 (16 vcpus, 112 GiB memory)
+* Worker VM: Standard F32s_v2 (32 vcpus, 64 GiB memory)
+
+
+The provisioned `OBS-Server` VM hosted all of the OBS services, dockerized to run easily and
+efficiently in a cloud environment. For the workers, we provisioned 3 `Worker` VMs, each VM running
+5 worker instances per architecture, with 3 architectures this resulted in a total of
+15 worker instances per virtual machine.
+In total, we ran 45 worker instances for our build farm. This includes 30 worker instances doing emulated
+builds, 15 for the 32-bit ARM architecture and 15 for the 64 bit architecture. The remaining 15 worker instances 
+were allocated for native `x86` builds.
+
+All services used Azure provided *Premium SSD* disk storage.
+Azure Networking was tweaked to allow full intercommunication in-between the VMs.
+
+The OBS Build setup was populated with the Apertis v2021dev3 release for the `development, target and sdk` components.
+The combined number of packages for the 3 repository components is: `4121`
+* developmet => 3237 packages
+* target => 465 packages
+* sdk => 419 packages
+
+Of the mentioned repositories, `development` and `target` repository are built for 3 architectures: `x86-64`, `armv7hl` and `aarch64`, while `sdk` repository is built only for the `x86-64` architecture.
+
+The full archive-wide rebuild of Apertis v2021dev3 was completed in around 1 week, with the above mentioned setup.
+There weren't any build failure specific to the setup above, to the `emulated build` setup in particular.
+Some packages failed to build while running their respective build time tests.
+
+To summazire, *Emulated Builds* worked fine with 2 caveats mentioned below
+* Performance: Given the emulation penalty, builds were 4-5 times slower than native.
+* Failing packages: Given the performance penalty due to emulation, some of the tests failed due to timeouts