On 06/16/2016 08:14 AM, Lukasz Anaczkowski wrote: > For reclaim this brings the performance back to before Mel's > flushing changes, but for unmap it disables batching.
This turns out to be pretty catastrophic for unmap. In a workload that uses, say 200 hardware threads and alloc/frees() a few MB/sec, this ends up costing hundreds of thousands of extra received IPIs. 10MB=~2500 ptes, and at with 200 threads, that's 250,000 IPIs received just to free 10MB of memory. The initial testing we did on this was on a *bunch* of threads all doing alloc/free. But this is bottlenecked on other things, like mmap_sem being held for write. The scenario that we really needed to test here was on lots of threads doing processing and 1 thread doing alloc/free.
