On Mon, Jul 13, 2020 at 09:46:31AM +0200, Christoph Hellwig wrote: > Hi all, > > this series has two parts: the first one picks up Dave's patch to avoid > invalidation entierly for reads, picked up deep down from the btrfs iomap > thread. The second one falls back to buffered writes if invalidation fails > instead of leaving a stale cache around. Let me know what you think about > this approch. Either we maintain application level concurrency for direct IOs and ignore the stale data in the page cache, or we kill application IO concurrency and keep the page cache coherent. It's a lose-lose choice and I'm on the fence as to which is the lesser of two evils. The main factor is whether the buffered IO fallback can be diagnosed. There's a new tracepoint for that case, so at least we will be able to tell if the fallback co-incides with application performance cratering. Hopefully this will only be a rare event. So, to hoist myself on my own petard: correctness first, performance second. Acked-by: Dave Chinner <dchinner@xxxxxxxxxx> Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
