[SRU][B/E/F][PATCH 0/1] LP:#1882039 - The thread level parallelism would be a bottleneck when searching for the shared pmd by using hugetlbfs

[Gavin Guo]

BugLink: https://bugs.launchpad.net/bugs/1882039

[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.


Waiman Long (1):
  hugetlbfs: take read_lock on i_mmap for PMD sharing

 mm/hugetlb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.17.1