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Daniel Jordan fe124c95df x86/mm: use max memory block size on bare metal 
Some of our servers spend significant time at kernel boot initializing
memory block sysfs directories and then creating symlinks between them and
the corresponding nodes.  The slowness happens because the machines get
stuck with the smallest supported memory block size on x86 (128M), which
results in 16,288 directories to cover the 2T of installed RAM.  The
search for each memory block is noticeable even with commit 4fb6eabf10
("drivers/base/memory.c: cache memory blocks in xarray to accelerate
lookup").

Commit 078eb6aa50 ("x86/mm/memory_hotplug: determine block size based on
the end of boot memory") chooses the block size based on alignment with
memory end.  That addresses hotplug failures in qemu guests, but for bare
metal systems whose memory end isn't aligned to even the smallest size, it
leaves them at 128M.

Make kernels that aren't running on a hypervisor use the largest supported
size (2G) to minimize overhead on big machines.  Kernel boot goes 7%
faster on the aforementioned servers, shaving off half a second.

[daniel.m.jordan@oracle.com: v3]
  Link: http://lkml.kernel.org/r/20200714205450.945834-1-daniel.m.jordan@oracle.com

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200609225451.3542648-1-daniel.m.jordan@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-12 10:57:57 -07:00
..
boot Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
configs x86/defconfigs: Refresh defconfig files 2020-07-25 12:02:14 +02:00
crypto crypto: x86/curve25519 - Remove unused carry variables 2020-07-31 18:25:29 +10:00
entry Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
events Misc cleanups all around the place. 2020-08-03 16:53:28 -07:00
hyperv
ia32 mm: remove unneeded includes of <asm/pgalloc.h> 2020-08-07 11:33:26 -07:00
include A set of locking fixes and updates: 2020-08-10 19:07:44 -07:00
kernel A set of locking fixes and updates: 2020-08-10 19:07:44 -07:00
kvm s390: implement diag318 2020-08-06 12:59:31 -07:00
lib
math-emu Merge branch 'work.regset' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 09:29:25 -07:00
mm x86/mm: use max memory block size on bare metal 2020-08-12 10:57:57 -07:00
net
oprofile
pci pci-v5.9-changes 2020-08-07 18:48:15 -07:00
platform mm: remove unneeded includes of <asm/pgalloc.h> 2020-08-07 11:33:26 -07:00
power Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
purgatory
ras
realmode
tools
um
video
xen A set of locking fixes and updates: 2020-08-10 19:07:44 -07:00
.gitignore
Kbuild
Kconfig s390: implement diag318 2020-08-06 12:59:31 -07:00
Kconfig.assembler
Kconfig.cpu
Kconfig.debug locking/lockdep: Fix TRACE_IRQFLAGS vs. NMIs 2020-07-27 15:13:29 +02:00
Makefile Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
Makefile.um
Makefile_32.cpu