Hi all,
As core counts are rapidly expanding over the next four years, Namhyung
and I were looking at global locks that we're already seeing high
contention on even today.
Some of these are not MM specific:
- cgroup_mutex
- cgroup_threadgroup_rwsem
- tasklist_lock
- kernfs_mutex (although should now be substantially better with the
kernfs_locks array)
Others *are* MM specific:
- list_lrus_mutex
- pcpu_drain_mutex
- shrinker_mutex (formerly shrinker_rwsem)
- vmap_purge_lock
- slab_mutex
This is only looking at fleet data for global static locks, not locks like
zone->lock that get dynamically allocated.
(mmap_lock was substantially improved by per-vma locking, although does
show up for very large vmas.)
Couple questions:
(1) How are people quantifying these pain points, if at all, in synthetic
testing? Any workloads or benchmarks that are really good at doing
this in the lab beyond the traditional will-it-scale? (The above is
from production data.)
(2) Is anybody working on any of the above global locks? Trying to
surface gaps for locks that will likely become even more painful in
the coming years.
Thanks!
