On Tuesday, July 6th, 2021 at 7:43 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Tue, Jul 6, 2021 at 4:46 PM Marc Zyngier maz@xxxxxxxxxx wrote: > > On Tue, 06 Jul 2021 15:30:34 +0100, Arnd Bergmann arnd@xxxxxxxx wrote: > > > I can only speculate on how much got reused between the two, but > > > as Falkor was released only after they had already given up on > > > the full-custom Kryo core, it's plausible that it incorporates bits from > > > that one. In particular the cache controller is probably easy to reuse > > > even if the rest of it was a new design. > > > > I guess we'll never find out, and I'm probably one of the few still > > having some access to this HW (not even sure for how long anyway). > > > > I won't cry if we decide to pull the plug on it. > > Sure, but the Snapdragon 820E is one we do need to worry about. > While the internet pretty much agrees on Falkor having 128 bytes > L1 cache line, it might be good to rule out that Kryo just misreports > it before we revert the patch. > > Yassine, could you run the 'line' and 'cache' helper from lmbench > to determine what the cache topology appears to be and if that > matches the CTR_EL0 contents? > > Something like > > numactl -C 0 line -M 1M > numactl -C 3 line -M 1M > numactl -C 0 cache > numactl -C 3 cache > > (the numactl command helps run this both on the 'big' and 'little' > cores without running into migration) > > Arnd Here are the results: $ numactl -C 0 line -M 1M 128 $ numactl -C 3 line -M 1M 128 $ numactl -C 0 cache L1 cache: 512 bytes 1.37 nanoseconds 64 linesize -1.00 parallelism L2 cache: 24576 bytes 2.75 nanoseconds 64 linesize 5.06 parallelism L3 cache: 131072 bytes 7.89 nanoseconds 64 linesize 3.85 parallelism L4 cache: 524288 bytes 15.86 nanoseconds 128 linesize 3.48 parallelism Memory latency: 145.93 nanoseconds 4.88 parallelism $ numactl -C 3 cache L1 cache: 24576 bytes 1.29 nanoseconds 64 linesize 5.00 parallelism L2 cache: 1048576 bytes 8.60 nanoseconds 128 linesize 3.07 parallelism Memory latency: 143.29 nanoseconds 5.37 parallelism
