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. Thanks. -- tejun