llnl / llnl/UnifyFS

Lustre group lock API

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enhancement
Dominant language
C
Stars
122
Forks
34
PR merge metrics
No merged PRs in 30d

Description

In Lustre, there is a way to declare that a set of processes all share a single write lock over the whole file. Processes are then responsible for ensuring that they don't step on each other when writing. One has to use close/sync to push data. One also has to write data on page boundaries. More details can be found here:

https://jira.whamcloud.com/browse/LU-15391

I have a simple test case that uses this API to test performance, though I need to update it based on the discussion in the noted ticket.

It is worth investigating how much performance one can get with this Lustre API call. If significant, then Lustre might also benefit from MPIX_File_fence. For example, when using collective I/O, the MPI library could acquire a group lock and gather data to be written on page boundaries on behalf of the user via collective buffering.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Read the linked LU-15391 discussion and locate the simple performance test case mentioned in the issue. Establish whether Lustre group locks provide a meaningful benefit and whether MPIX_File_fence or collective-I/O integration should be pursued; done requires benchmark results and a decided scope.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
operating-systems, performance
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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