** Changed in: linux (Ubuntu)
Assignee: (unassigned) => ChengEn, Du (chengendu)
** Changed in: linux (Ubuntu)
Status: Incomplete => In Progress
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https://bugs.launchpad.net/bugs/2015827
Title:
NFS performance issue while clearing the file access cache upon login
Status in linux package in Ubuntu:
In Progress
Bug description:
The performance issue that has been observed may be attributed to an increase
in NFS ACCESS operations, possibly due to a new mechanism introduced in the
Linux 6.2-rc3 NFS client side.
This mechanism clears the access cache as soon as the cache timestamp becomes
older than the user's login time,
with the primary objective of preventing the NFS client's access cache from
becoming stale due to any changes made to the user's group membership on the
server after the user has already logged in on the client.
It's worth noting that POSIX only refreshes the user's supplementary group
information upon login.
Upstream has taken into consideration that users may reasonably expect the
access cache to be cleared when they log out and log back in again, with all
behavior returning to normal after the replacement.
The performance overhead can be particularly noticeable when applications or
users switch to other privileged users via commands such as "su" to operate on
NFS-mounted folders.
In such cases, the privileged user's login time will be renewed, and NFS
ACCESS operations will need to be re-sent, potentially leading to performance
degradation.
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