commit 02829da5fd99da9965bbb9c6d00962f32f2508a8
author A. Cody Schuffelen <schuffelen@google.com> Sat Jun 17 01:43:27 2023 -0700
committer A. Cody Schuffelen <schuffelen@google.com> Sat Jun 17 01:43:27 2023 -0700
tree 00728d1f178833841f27cbaf691b91edf0e478a9
parent 2cd328fdf17c1bf0f979bf4c728538f6edb0761e

BACKPORT: Add `--core-scheduling` flag gating interaction with PR_SCHED_CORE

On Android CI we observe performance regressions when crosvm takes
advantage of the PR_SCHED_CORE feature. We are somewhat oversubscribed
on CPUs, in some cases running a Cuttlefish Android VM with --cpus=4 and
an OpenWRT VM with --cpus=1 next to some other host processes on cloud
instances with 2 cores and 4 hyperthreads. In this case we would prefer
not to lose cpu time to the scheduler blocking off hyperthreads when
either VM claims complete cores to itself.

In this case we are intending to fall back to the default state of "all
processes trust each other", mentioned under "Trust model" on
https://www.kernel.org/doc/html/next/admin-guide/hw-vuln/core-scheduling.html

`--core-scheduling` defaults to true, so there is no behavioral
change for existing users.

Bug: b/280660768
Test: `crosvm start --core-scheduling=false` from Cuttlefish launcher script
Change-Id: Id154790c16b7d9f81aff1f189468959fb5fa7259
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4602908
Reviewed-by: Frederick Mayle <fmayle@google.com>
Reviewed-by: Dennis Kempin <denniskempin@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Commit-Queue: Cody Schuffelen <schuffelen@google.com>
Merged-In: Id154790c16b7d9f81aff1f189468959fb5fa7259