Skip to content

concurrency limit 64 -> 10 #3578

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
wants to merge 2 commits into
base: main
Choose a base branch
from
+10 −5
Draft

concurrency limit 64 -> 10 #3578

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
f89ba54
concurrency limit 64 -> 10
d-v-b Nov 10, 2025
9ac0e6b
update reference to concurrency limit in docs
d-v-b Nov 10, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
11 changes: 8 additions & 3 deletions docs/user-guide/performance.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -175,13 +175,18 @@ Coming soon.

## Parallel computing and synchronization

Zarr is designed to support parallel computing and enables concurrent reads and writes to arrays. This section covers how to optimize Zarr's concurrency settings for different parallel computing scenarios.
Zarr is designed to support parallel computing and enables concurrent reads and writes to arrays.
This section covers how to optimize Zarr's concurrency settings for different parallel computing
scenarios.

### Concurrent I/O operations

Zarr uses asynchronous I/O internally to enable concurrent reads and writes across multiple chunks. The level of concurrency is controlled by the `async.concurrency` configuration setting, which determines the maximum number of concurrent I/O operations.
Zarr uses asynchronous I/O internally to enable concurrent reads and writes across multiple chunks.
The level of concurrency is controlled by the `async.concurrency` configuration setting, which
determines the maximum number of concurrent I/O operations.

The default value is 64, which provides good performance for most workloads. You can adjust this value based on your specific needs:
The default value is 10, which is a conservative value. You may get improved performance by tuning
the concurrency limit. You can adjust this value based on your specific needs:

```python
import zarr
Expand Down
2 changes: 1 addition & 1 deletion src/zarr/core/config.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -97,7 +97,7 @@ def enable_gpu(self) -> ConfigSet:
"order": "C",
"write_empty_chunks": False,
},
"async": {"concurrency": 64, "timeout": None},
"async": {"concurrency": 10, "timeout": None},
"threading": {"max_workers": None},
"json_indent": 2,
"codec_pipeline": {
Expand Down
2 changes: 1 addition & 1 deletion tests/test_config.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,7 @@ def test_config_defaults_set() -> None:
"order": "C",
"write_empty_chunks": False,
},
"async": {"concurrency": 64, "timeout": None},
"async": {"concurrency": 10, "timeout": None},
"threading": {"max_workers": None},
"json_indent": 2,
"codec_pipeline": {
Expand Down
Loading