Will, On 22.09.15 19:29:02, Will Deacon wrote: > On Tue, Sep 22, 2015 at 06:59:48PM +0100, Robert Richter wrote: > > From: Tirumalesh Chalamarla <[email protected]> > > > > Increase the standard cacheline size to avoid having locks in the same > > cacheline. > > > > Cavium's ThunderX core implements cache lines of 128 byte size. With > > current granulare size of 64 bytes (L1_CACHE_SHIFT=6) two locks could > > share the same cache line leading a performance degradation. > > Increasing the size fixes that. > > Do you have an example of that happening?
I did some 'poor man's kernel build all modules benchmarking' and could not find significant performance improvements so far (second part with the patch reverted): build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m10.490s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.747s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.264s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m0.435s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.569s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.274s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m0.507s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m1.551s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 6m59.073s build-allmodules-4.2.0-01404-g5818d6e89783.log:real 7m1.738s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m10.644s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.814s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.315s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.610s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.885s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 6m59.281s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.869s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.953s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.787s build-allmodules-4.2.0-01406-g638c69fddc40.log:real 7m0.656s I will check what kind of workloads this patch was written for. Tirumalesh, any idea? Thanks, -Robert > > > Increasing the size has no negative impact to cache invalidation on > > systems with a smaller cache line. There is an impact on memory usage, > > but that's not too important for arm64 use cases. > > Do you have any before/after numbers to show the impact of this change > on other supported SoCs? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
