Re: HIGHMEM64G Kernel (2.6.23.1) makes system crawl

[Boaz Harrosh <bharrosh@panasas.com>]

On Wed, Oct 24 2007 at 12:26 +0200, "Rajkumar S" <rajkumars@gmail.com> wrote:
> Hello,
> 
> I am using a Core 2 Duo E6750 CPU on an intel DG33FB mother board with
> 4GB Ram, running Debian Lenny.
> 
> Since the box has 4 GB ram I compiled a big mem kernel, but the
> machine is very slow while running big mem kernel. It takes about 37
> minutes to compile the intel e1000 driver  (e1000-7.6.5.tar.gz) from
> intel site. But it's performing normally when using a non big mem
> kernel. The diff of the .config between working and non working is as
> follows.
> 
> --- config-nobigmem     2007-10-24 12:51:42.000000000 +0530
> +++ config-bigmem       2007-10-24 12:48:56.000000000 +0530
> @@ -1,7 +1,7 @@
>  #
>  # Automatically generated make config: don't edit
>  # Linux kernel version: 2.6.23.1
> -# Wed Oct 24 12:50:21 2007
> +# Tue Oct 23 18:08:30 2007
>  #
>  CONFIG_X86_32=y
>  CONFIG_GENERIC_TIME=y
> @@ -189,10 +189,11 @@
>  CONFIG_DELL_RBU=m
>  CONFIG_DCDBAS=m
>  CONFIG_DMIID=y
> -CONFIG_NOHIGHMEM=y
> +# CONFIG_NOHIGHMEM is not set
>  # CONFIG_HIGHMEM4G is not set
> -# CONFIG_HIGHMEM64G is not set
> +CONFIG_HIGHMEM64G=y
>  CONFIG_PAGE_OFFSET=0xC0000000
> +CONFIG_HIGHMEM=y
>  CONFIG_X86_PAE=y
>  CONFIG_ARCH_FLATMEM_ENABLE=y
>  CONFIG_ARCH_SPARSEMEM_ENABLE=y
> @@ -211,6 +212,7 @@
>  CONFIG_BOUNCE=y
>  CONFIG_NR_QUICK=1
>  CONFIG_VIRT_TO_BUS=y
> +# CONFIG_HIGHPTE is not set
>  # CONFIG_MATH_EMULATION is not set
>  CONFIG_MTRR=y
>  CONFIG_EFI=y
> @@ -223,11 +225,13 @@
>  # CONFIG_HZ_1000 is not set
>  CONFIG_HZ=250
>  CONFIG_KEXEC=y
> +# CONFIG_CRASH_DUMP is not set
>  CONFIG_PHYSICAL_START=0x100000
>  # CONFIG_RELOCATABLE is not set
>  CONFIG_PHYSICAL_ALIGN=0x100000
>  CONFIG_HOTPLUG_CPU=y
>  CONFIG_COMPAT_VDSO=y
> +CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y
> 
>  #
>  # Power management options (ACPI, APM)
> @@ -1283,6 +1287,7 @@
>  CONFIG_I2O=m
>  CONFIG_I2O_LCT_NOTIFY_ON_CHANGES=y
>  CONFIG_I2O_EXT_ADAPTEC=y
> +CONFIG_I2O_EXT_ADAPTEC_DMA64=y
>  CONFIG_I2O_CONFIG=m
>  CONFIG_I2O_CONFIG_OLD_IOCTL=y
>  CONFIG_I2O_BUS=m
> @@ -3323,6 +3328,7 @@
>  # CONFIG_DEBUG_SPINLOCK_SLEEP is not set
>  # CONFIG_DEBUG_LOCKING_API_SELFTESTS is not set
>  # CONFIG_DEBUG_KOBJECT is not set
> +# CONFIG_DEBUG_HIGHMEM is not set
>  CONFIG_DEBUG_BUGVERBOSE=y
>  # CONFIG_DEBUG_INFO is not set
>  # CONFIG_DEBUG_VM is not set
> 
> I was having this same issue with debian kernel also (2.6.22-2-686),
> ie stock kernel will work, but big mem is slow. Which is why I tried
> latest kernel.
> 
> I am posting the full .config at http://pastebin.ca/747758 dmesg while
> booting big mem kernel is at http://pastebin.ca/747766
> 
> raj

I thought that for 4GB of memory the CONFIG_HIGHMEM4G=y CONFIG_HIGHMEM64G is not set
would be enough.

>From looking in source code the CONFIG_HIGHMEM64G is broken in many respects,
in my opinion. It's really a 64-bit with 32-bit quirks enabled. Does it even
run on None 64-bit machines? Not many! 

You have a magnificent 64-bit Machine, why?

Boaz