On Tue, Mar 23, 2021 at 09:27:38PM -0700, Aruna Ramakrishna wrote: > > Do you have benchmarks that show the performance of the high order > > pages is not relavent? I'm a bit surprised to hear that > > > > I guess my point was more to the effect that an order-8 alloc will > fail more often than not, in this flow. For instance, when we were > debugging the latency spikes here, this was the typical buddyinfo > output on that system: > > Node 0, zone DMA 0 1 1 2 3 0 1 0 > 1 1 3 > Node 0, zone DMA32 7 7 7 6 10 2 6 7 > 6 2 306 > Node 0, zone Normal 3390 51354 17574 6556 1586 26 2 1 > 0 0 0 > Node 1, zone Normal 11519 23315 23306 9738 73 2 0 1 > 0 0 0 > > I think this level of fragmentation is pretty normal on long running > systems. Here, in the reg_mr flow, the first try (order-8) alloc > will probably fail 9 times out of 10 (esp. after the addition of > GFP_NORETRY flag), and then as fallback, the code tries to allocate > a lower order, and if that too fails, it allocates a page. I think > it makes sense to just avoid trying an order-8 alloc here.
But a system like this won't get THPs either, so I'm not sure it is relevant. The function was designed as it is to consume a "THP" if it is available. Jason
