On Tue, Sep 13, 2016 at 10:14:20AM +0300, Riku Voipio wrote: > Hi, Hi,
> As painfully found out by mono team, if big/little cores have > different cache line sizes, __clear_cache doesn't work as expected. > This affects any home-grown cache flushing mechanism as well. > > http://www.mono-project.com/news/2016/09/12/arm64-icache/ > > protip, if you suspect your application issues might related to > big.LITTLE, use taskset(1) or hwloc-bind(1) to tie the process to > either big or little cluster (or just a single core). While this is a real bug, the conclusions in the article aren't quite right, so I'd like to clarify a few things before this spreads further: * This only affects a single SoC, and is not a generic issue with big.LITTLE. Correctly-written software following the sequences in the ARM ARM will work on all other platforms. * This mismatch is in violation of the architecture (i.e. it is a hardware bug), so hopefully more instances of this will not be seen in future. * Upstream, there is a kernel patch [1] in discussion, which will work around this issue in the kernel, transparently to userspace. * Setting affinity and/or caching the minimum value in userspace is racy with hotplug (as used on Android for power management). While useful for testing it does not solve the issue. Thanks, Mark. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-September/455679.html _______________________________________________ linaro-toolchain mailing list linaro-toolchain@lists.linaro.org https://lists.linaro.org/mailman/listinfo/linaro-toolchain
