Hello, Doug. On Wed, May 01, 2019 at 10:44:31AM -0400, Doug Ledford wrote: > The discussion is helpful, but we still need to decide on the patch: > > Correct me if I'm wrong Tejun, but the key issues are: > > All WQ_MEM_RECLAIM work queues are eligible to be run when the machine > is under extreme memory pressure and attempting to reclaim memory. That > means that the workqueue: > > 1) MUST not perform any GFP_ATOMIC allocations as this could deadlock GFP_ATOMIC or GFP_NOIO allocations are fine as they wouldn't block on reclaim recursively; however, they can and will fail under severe memory pressure. > 2) SHOULD not rely on any GFP_KERNEL allocations as these may fail Absolutely not, but not because they may fail but because it can end up creating a waiting loop. > 3) MUST complete without blocking Blocking is fine as long as that blocking isn't memory bound. > 4) SHOULD ideally always make some sort of forward progress if at all > possible without needing memory allocations to do so Yes, this is the only requirement. All restrictions stem from this one. Thanks. -- tejun
