[LU-6580] Poor read performance with many ptlrpcd threads on the client

• Type: Bug
• Resolution: Duplicate
• Priority: Major
• Affects Version/s: Lustre 2.7.0
• Severity: 3
• Assignee: Dmitry Eremin (Inactive)
• Reporter: Sebastien Buisson (Inactive)

Description

Hi,

With Lustre 2.7.0, we have noticed a very bad impact of the number of ptlrpcd threads on the client over the data read performance.
If the number of ptlrpcd threads on the client is set to its default value which is the number of cores, then we have a drop in performance of almost 20%, compared to the case where we reduce the number of ptlrpcd threads to 1/3 of the number of cores.

For instance see the results attached to this ticket. We use IOR with 24 tasks on a Lustre client node with 24 cores and one Infiniband FDR interface.

What can explain this phenomenon in Lustre 2.7.0, as we do not see it with Lustre 2.5 and 2.6?
Do you consider this is a bug, or a behavior change due to some modifications in Lustre 2.7 code (in that case we would like to learn more about)?

Thanks in advance,
Sebastien.

Issue Links

• is related to: LU-6325 CPT bound ptlrpcd's are unimplemented