On 5/5/20 8:07 AM, SeongJae Park wrote: > On Tue, 5 May 2020 07:53:39 -0700 Eric Dumazet <edumazet@xxxxxxxxxx> wrote: > >> Why do we have 10,000,000 objects around ? Could this be because of >> some RCU problem ? > > Mainly because of a long RCU grace period, as you guess. I have no idea how > the grace period became so long in this case. > > As my test machine was a virtual machine instance, I guess RCU readers > preemption[1] like problem might affected this. > > [1] https://www.usenix.org/system/files/conference/atc17/atc17-prasad.pdf > >> >> Once Al patches reverted, do you have 10,000,000 sock_alloc around ? > > Yes, both the old kernel that prior to Al's patches and the recent kernel > reverting the Al's patches didn't reproduce the problem. > I repeat my question : Do you have 10,000,000 (smaller) objects kept in slab caches ? TCP sockets use the (very complex, error prone) SLAB_TYPESAFE_BY_RCU, but not the struct socket_wq object that was allocated in sock_alloc_inode() before Al patches. These objects should be visible in kmalloc-64 kmem cache.
