fix(config): Use CONFIG_HZ=1000 consistently - #256
Merged
Merged
Conversation
The default value for the Linux `CONFIG_HZ` setting is 1000. We have been using this value for the Edera host kernels, but it is currently set to `CONFIG_HZ=100` for zone kernels. When compared with running on bare-metal or with LXC as the container engine, this lower rate of ticks was found to be causing performance impact in a benchmark that issues a high rate of `docker run` invocations (modelling a prospect's workload). The more vCPUs that are added to an Edera zone, the worse the benchmark performs, with almost 4x the runtime (at 96 vCPUs) compared to bare metal or LXC. The likely culprit is contention around a global process ID lock in `copy_process()` and `do_exit()`. Using `CONFIG_HZ=1000`, matching both the Linux kernel defaults as well as e.g. the Ubuntu kernel configuration, completely resolves the performance impact. Apply this value uniformly across host and zone kernels across all architectures. Part-of: https://linear.app/edera/issue/PRT-477/customer-zero-performance-gap-observed-in-edera-vs-lxc-when-testing Signed-off-by: Simon Veith <simon@edera.dev>
sveith
requested review from
alexandermerritt,
azenla,
bleggett,
kaniini and
tycho
as code owners
September 17, 2026 12:27
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The default value for the Linux
CONFIG_HZsetting is 1000. We havebeen using this value for the Edera host kernels, but it is currently
set to
CONFIG_HZ=100for zone kernels.When compared with running on bare-metal or with LXC as the container
engine, this lower rate of ticks was found to be causing performance
impact in a benchmark that issues a high rate of
docker runinvocations (modelling a prospect's workload).
The more vCPUs that are added to an Edera zone, the worse the benchmark
performs, with almost 4x the runtime (at 96 vCPUs) compared to bare
metal or LXC. The likely culprit is contention around a global process
ID lock in
copy_process()anddo_exit().Using
CONFIG_HZ=1000, matching both the Linux kernel defaults as wellas e.g. the Ubuntu kernel configuration, completely resolves the
performance impact. Apply this value uniformly across host and zone
kernels across all architectures.
Part-of: https://linear.app/edera/issue/PRT-477/customer-zero-performance-gap-observed-in-edera-vs-lxc-when-testing
Signed-off-by: Simon Veith simon@edera.dev