document memmap option better and help people with bad memory

Provide example for memmap exclude option (it is slightly strange an
non-trivial) and provide nice small HOWTO for people with bad memory.

Signed-off-by: Jan-Simon Moeller <dl9pf@xxxxxx>
Signed-off-by: Pavel Machek <pavel@xxxxxxx>

---
commit ec630f2291d7a3a154e22fa54cd74e5f6aa47f9a
tree 9cf33f9fcda3ea363061acebc971c37815f6c907
parent 456fc99ea933d38466ee25681908868cde3425c5
author Pavel <pavel@xxxxxxxxxx> Thu, 13 Mar 2008 09:06:15 +0100
committer Pavel <pavel@xxxxxxxxxx> Thu, 13 Mar 2008 09:06:15 +0100

Documentation/bad_memory.txt | 45 +++++++++++++++++++++++++++++++++++
Documentation/kernel-parameters.txt | 4 +++
2 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/Documentation/bad_memory.txt b/Documentation/bad_memory.txt
new file mode 100644
index 0000000..df84162
--- /dev/null
+++ b/Documentation/bad_memory.txt
@@ -0,0 +1,45 @@
+March 2008
+Jan-Simon Moeller, dl9pf@xxxxxx
+
+
+How to deal with bad memory e.g. reported by memtest86+ ?
+#########################################################
+
+There are three possibilities I know of:
+
+1) Reinsert/swap the memory modules
+
+2) Buy new modules (best!) or try to exchange the memory
+ if you have spare-parts
+
+3) Use BadRAM or memmap
+
+This Howto is about number 3) .
+
+
+BadRAM
+######
+BadRAM is the actively developed and available as kernel-patch
+here: http://rick.vanrein.org/linux/badram/
+
+For more details see the BadRAM documentation.
+
+memmap
+######
+
+memmap is already in the kernel and usable as kernel-parameter at
+boot-time. Its syntax is slightly strange and you may need to
+calculate the values by yourself!
+
+Syntax to exclude a memory area (see kernel-parameters.txt for details):
+memmap=<size>$<address>
+
+Example: memtest86+ reported here errors at address 0x18691458, 0x18698424 and
+ some others. All had 0x1869xxxx in common, so I chose a pattern of
+ 0x18690000,0xffff0000.
+
+With the numbers of the example above:
+memmap=64K$0x18690000
+ or
+memmap=0x10000$0x18690000
+
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 533e67f..f25da88 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1131,6 +1131,10 @@ and is between 256 and 4096 characters.
memmap=nn[KMG]$ss[KMG]
[KNL,ACPI] Mark specific memory as reserved.
Region of memory to be used, from ss to ss+nn.
+ Example: Exclude memory from 0x18690000-0x1869ffff
+ memmap=64K$0x18690000
+ or
+ memmap=0x10000$0x18690000

meye.*= [HW] Set MotionEye Camera parameters
See Documentation/video4linux/meye.txt.

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages

  • Re: Document hadling of bad memory
    ... Document how to deal with bad memory reported with memtest. ... +3) Use BadRAM or memmap ... +BadRAM is the actively developed and available as kernel-patch ...
    (Linux-Kernel)
  • Re: [PATCH] x86 Boot NUMA kernels on non-NUMA hardware with DISCONTIG memory model
    ... entries for the memmap. ... memory area normally occupied by the end of low memory. ... problem before in the years that this code has been in the kernel. ... that a little memory is wasted when this kernel is used on a non-NUMA ...
    (Linux-Kernel)
  • Re: numpy.memmap advice?
    ... In other words, given a huge file, a memmap object ... amount of memory is allocated for the memmap operation, ... memory allocation occurs when I generate my final numpy sub-array by ... in the mmap. ...
    (comp.lang.python)
  • Re: numpy.memmap advice?
    ... In other words, given a huge file, a memmap object ... amount of memory is allocated for the memmap operation, ... memory allocation occurs when I generate my final numpy sub-array by ... in the mmap. ...
    (comp.lang.python)
  • Re: numpy.memmap advice?
    ... In other words, given a huge file, a memmap object ... amount of memory is allocated for the memmap operation, ... memory allocation occurs when I generate my final numpy sub-array by ...  There is no copying data or separate array allocation.. ...
    (comp.lang.python)