On Mon, 2020-11-09 at 09:01 -0500, t...@kernel.org wrote: > Hello, > > On Mon, Nov 09, 2020 at 01:50:40PM +0000, Trond Myklebust wrote: > > > I'm thinking the real problem is that you're abusing workqueues. > > > Just > > > don't stuff so much work into it that this becomes a problem. Or > > > rather, > > > if you do, don't lie to it about it. > > > > If we can't use workqueues to call iput_final() on an inode, then > > what > > is the point of having them at all? > > > > Neil's use case is simply a file that has managed to accumulate a > > seriously large page cache, and is therefore taking a long time to > > complete the call to truncate_inode_pages_final(). Are you saying > > we > > have to allocate a dedicated thread for every case where this > > happens? > > I think the right thing to do here is setting CPU_INTENSIVE or using > an > unbound workqueue. Concurrency controlled per-cpu workqueue is > unlikely to > be a good fit if the work can run long enough to need cond_resched(). > Better > to let the scheduler handle it. Making workqueue warn against long- > running > concurrency managed per-cpu work items would be great. I'll put that > on my > todo list but if anyone is interested please be my guest. >
That means changing all filesystem code to use cpu-intensive queues. As far as I can tell, they all use workqueues (most of them using the standard system queue) for fput(), dput() and/or iput() calls. -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.mykleb...@hammerspace.com
