On Thu, Jan 22, 2015 at 11:03:00AM +0000, Arnd Bergmann wrote: > Unrelated to this question however is whether we want to keep > supersection mappings as a performance optimization to save TLBs. > It seems useful to me, but not critical. Currently in Linux we allow 16MB mappings only if the phys address is over 32-bit and !LPAE which makes it unlikely for normal RAM with pre-LPAE hardware. IIRC a bigger problem was that supersections are optional in the architecture but there was no CPUID bit field in ARMv6 (and early ARMv7) to check for their presence. The ID_MMFR3 contains this information but for example on early Cortex-A8 that bitfield was reserved and the TRM states "unpredictable" on read (so probably zero in practice). On newer ARMv7 (not necessarily with LPAE), we could indeed revisit the 16MB section mapping but it won't go well with single zImage if you want to support earlier ARMv7 or ARMv6. -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>