On Thu, Oct 17, 2024 at 12:19:58AM -0500, Cristian Prundeanu wrote:

For example, running mysql+hammerdb results in a 12-17% throughput 

Gautham, is this a benchmark you're running?

Testing combinations of available scheduler features showed that the 
largest improvement (short of disabling all EEVDF features) came from 
disabling both PLACE_LAG and RUN_TO_PARITY:

How does using SCHED_BATCH compare?

While the long term approach is debugging and fixing the scheduler 
behavior, algorithm changes to address performance issues of this nature 
are specialized (and likely prolonged or open-ended) research. Until a 
change is identified which fixes the performance degradation, in the 
interest of a better out-of-the-box performance: (1) disable these 
features by default, and (2) expose these values in sysctl instead of 
debugfs, so they can be more easily persisted across reboots.

So disabling them by default will undoubtedly affect a ton of other
workloads. And sysctl is arguably more of an ABI than debugfs, which
doesn't really sound suitable for workaround.

And I don't see how adding a line to /etc/rc.local is harder than adding
a line to /etc/sysctl.conf