[Bug 1882039] Re: The thread level parallelism would be a bottleneck when searching for the shared pmd by using hugetlbfs

** Changed in: linux (Ubuntu Bionic)
Status: In Progress => Fix Committed

** Changed in: linux (Ubuntu Eoan)
Status: In Progress => Fix Committed

** Changed in: linux (Ubuntu Focal)
Status: In Progress => Fix Committed

--
You received this bug notification because you are subscribed to linux
in Ubuntu.
Matching subscriptions: Bgg, Bmail, Nb
https://bugs.launchpad.net/bugs/1882039

Title:
The thread level parallelism would be a bottleneck when searching for
the shared pmd by using hugetlbfs

Status in linux package in Ubuntu:
In Progress
Status in linux source package in Bionic:
Fix Committed
Status in linux source package in Eoan:
Fix Committed
Status in linux source package in Focal:
Fix Committed

Bug description:
[Impact]

There is performance overhead observed when many threads
are using hugetlbfs in the database environment.

[Fix]

bdfbd98bc018 hugetlbfs: take read_lock on i_mmap for PMD sharing

The patch improves the locking by using the read lock instead of the
write lock. And it allows multiple threads searching the suitable shared
VMA. As there is no modification inside the searching process. The
improvement increases the parallelism and decreases the waiting time of
the other threads.

[Test]

The customer stand-up a database with seed data. Then they have a
loading "driver" which makes a bunch of connections that look like user
workflows from the database perspective. Finally, the measuring response
times improvement can be observed for these "users" as well as various
other metrics at the database level.

[Regression Potential]

The modification is only in replacing the write lock to a read one. And
there is no modification inside the loop. The regression probability is
low.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1882039/+subscriptions