Re: Memory restrictions

Christian Christmann wrote:
Hi,

someone told me that in a typical Linux configuration,
single process can not allocate more than about 1.5GB due
to memory layout restrictions.

Is that true?

Not that I know of. For the usual 32-bit kernels, the limit is around 3.5
GBytes, IIRC. If you use a kernel set up right (e.g., Red Hat Enterprise
Linux 3) and have some parameters set like this in the .config file for the
kernel,

# CONFIG_NOHIGHMEM is not set
# CONFIG_HIGHMEM4G is not set
CONFIG_HIGHMEM64G=y <---<<<
CONFIG_HIGHMEM=y
CONFIG_HIGHPTE=y
CONFIG_X86_PAE=y
CONFIG_HIGHIO=y
CONFIG_X86_4G=y <---<<<
CONFIG_X86_SWITCH_PAGETABLES=y
CONFIG_X86_4G_VM_LAYOUT=y
CONFIG_X86_UACCESS_INDIRECT=y
CONFIG_X86_HIGH_ENTRY=y

you can go up to 4G per process. You would want at least 8G RAM to do this.

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