Messages in this thread | | | Subject | Re: [mm] 2d146aa3aa: vm-scalability.throughput -36.4% regression | From | Andi Kleen <> | Date | Wed, 1 Sep 2021 19:23:24 -0700 |
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On 9/1/2021 6:35 PM, Feng Tang wrote: > On Wed, Sep 01, 2021 at 08:12:24AM -0700, Andi Kleen wrote: >> Feng Tang <feng.tang@intel.com> writes: >>> Yes, the tests I did is no matter where the 128B padding is added, the >>> performance can be restored and even improved. >> I wonder if we can find some cold, rarely accessed, data to put into the >> padding to not waste it. Perhaps some name strings? Or the destroy >> support, which doesn't sound like its commonly used. > Yes, I tried to move 'destroy_work', 'destroy_rwork' and 'parent' over > before the 'refcnt' together with some padding, it restored the performance > to about 10~15% regression. (debug patch pasted below) > > But I'm not sure if we should use it, before we can fully explain the > regression.
Narrowing it down to a single prefetcher seems good enough to me. The behavior of the prefetchers is fairly complicated and hard to predict, so I doubt you'll ever get a 100% step by step explanation.
-Andi
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