On Thursday 03 April 2008 07:55:25 pm Robert P. J. Day wrote: > > given that i'm determined to nail down how linux MM works, i'm > perusing the code and some docs from the beginning and, since a lot of > those docs annoyingly disagree with each other in some fundamental > places, i'm going to be asking some annoyingly trivial questions. get > used to it. :-) > > to start, the standard definition of high memory on a 32-bit x86 > system is memory above 896M. > > * where is that exact boundary defined? > Hi Robert, Out of the 1G logical address space the kernel sees, 128MB is eaten up by VMALLOC_RESERVE for establishing (temporary) mappings into high memory, leaving only 896 MB as low memory. The definition for that 128 MB is found in arch/x86/mm/init_32.c as unsigned int __VMALLOC_RESERVE = 128 << 20; > * can it be changed at kernel config time? Apparently it can't be changed.. Does this answer your question ? regards, balaji rao -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
