On Tue, May 26, 2020 at 04:30:58PM -0400, Waiman Long wrote: > On 5/26/20 3:56 PM, Peter Zijlstra wrote: > > On Tue, May 26, 2020 at 02:58:50PM -0400, Qian Cai wrote: > > > > > I still don't understand why reading all sysfs files on this system > > > could increase that much, but here is the lockdep file after > > > running sysfs read to see if you could spot anything obviously, > > > > > > https://cailca.github.io/files/lockdep.txt > > 00000000f011a2a5 OPS: 20 FD: 45 BD: 1 .+.+: kn->active#834 > > > > is that somewhere near the number of CPUs you have? > > > > Anyway, there's very long "kn->active#..." chains in there, which seems > > to suggest some annotation is all sorts of buggered. > > > It is actually one active lock per instance of the kerfs_node structures. > That means more than 800 sysfs files are accessed in some way. As we could > have much more than 800 sysfs files in the system, we could easily overwhelm > the lockdep tables if we really try to access all of them.
Yes, there are a lot of those on large systems, NUMA, percpu, slab etc. Isn't it better to extend MAX_LOCKDEP_ENTRIES dynamically? There are plenty of memory over there.