[LU-3631] file stats are slow on filesystem start up

• Type: Bug
• Resolution: Not a Bug
• Priority: Trivial
• Affects Version/s: Lustre 1.8.9
• Severity: 3
• Assignee: Oleg Drokin
• Reporter: Kit Westneat (Inactive)

Description

NOAA had a question about an observed behavior. As part of their change management validation, they rerun a battery of tests after they make a change. One of those is mdtest. What has been observed is that after a downtime, the file stat performance is terrible. Like 400/s. After a while, it goes up to around 10-15k. It seems to be a function of load as opposed to time. The more the filesystem is used (due to other testing), the faster the stat performance increases.

Are there any thoughts on why this might happen? I have tried preloading the OST metadata, but that didn't seem to have any effect. I thought that IB routing might be an issue, but even when the IB fabric is untouched, we see this issue. It seems like it must be a cache issue, but I am unsure what caches are being warmed up. Any insight on why we are seeing this and how to preload the cache would be great.

Thanks.

Issue Links

• is related to: LU-10967 MDT page cache management improvements