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mm: provide kernel parameter to allow disabling page init poisoning

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Patch series "Address issues slowing persistent memory initialization", v5.

The main thing this patch set achieves is that it allows us to initialize
each node worth of persistent memory independently.  As a result we reduce
page init time by about 2 minutes because instead of taking 30 to 40
seconds per node and going through each node one at a time, we process all
4 nodes in parallel in the case of a 12TB persistent memory setup spread
evenly over 4 nodes.

This patch (of 3):

On systems with a large amount of memory it can take a significant amount
of time to initialize all of the page structs with the PAGE_POISON_PATTERN
value.  I have seen it take over 2 minutes to initialize a system with
over 12TB of RAM.

In order to work around the issue I had to disable CONFIG_DEBUG_VM and
then the boot time returned to something much more reasonable as the
arch_add_memory call completed in milliseconds versus seconds.  However in
doing that I had to disable all of the other VM debugging on the system.

In order to work around a kernel that might have CONFIG_DEBUG_VM enabled
on a system that has a large amount of memory I have added a new kernel
parameter named "vm_debug" that can be set to "-" in order to disable it.

Link: http://lkml.kernel.org/r/20180925201921.3576.84239.stgit@localhost.localdomain
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexander Duyck
2018-10-26 15:07:45 -07:00
committed by Linus Torvalds
parent 85cfb24506
commit f682a97a00
5 changed files with 69 additions and 6 deletions
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12
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -4839,6 +4839,18 @@
This is actually a boot loader parameter; the value is
passed to the kernel using a special protocol.
vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
May slow down system boot speed, especially when
enabled on systems with a large amount of memory.
All options are enabled by default, and this
interface is meant to allow for selectively
enabling or disabling specific virtual memory
debugging features.
Available options are:
P Enable page structure init time poisoning
- Disable all of the above options
vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
size of <nn>. This can be used to increase the
minimum size (128MB on x86). It can also be used to