On Thu, Nov 22, 2018 at 07:16:32AM -0800, Matthew Wilcox wrote: > Yes, your allocations from the page_frag allocator have to have similar > lifetimes. I thought that would be ideal for XFS though; as I understood > the problem, these were per-IO allocations, and IOs to the same filesystem > tend to take roughly the same amount of time. Sure, in an error case, > some IOs will take a long time before timing out, but it should be OK > to have pages unavailable during that time in these rare situations. > What am I missing? No, thee are allocations for meatada buffers, which can stay around for a long time. Worse still that depends on usage, so one buffer allocated from ma page might basically stay around forever, while another one might get reclaimed very quickly.
