On 10/10/2013 05:22 AM, H. Peter Anvin wrote: > On 10/09/2013 02:19 PM, Zhang Yanfei wrote: >>> >>> Yeah, I was referring to the 16MB limit, which apparently ceased to >>> exist. >> >> Hmmmm...If we are talking 16MB limit hear, I don't think it a problem, either. >> Currently, default loading & running address of kernel is 16MB, so the >> kernel itself is above 16MB, memory allocated in bottom-up mode is obviously >> above the 16MB. Just seeing from a RHEL6.3 server: >> >> 01000000-01507ff4 : Kernel code >> 01507ff5-01c07b2f : Kernel data >> 01d4e000-02012023 : Kernel bss >> >> IOW, even if kernel is loaded and running at 1MB, it self will occupy about >> 16MB from the above. >> > > For various DMA devices you can find almost every possible power of 2 > being a limitation. The most common limits are 24, 32, and 40 bits, but > you also see odd ones like 30 bits in the field. Really. > Thanks for this. I was always curious about what the limit is when we said DMA limit before. -- Thanks. Zhang Yanfei -- 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>