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authorDaniel Jordan <daniel.m.jordan@oracle.com>2020-08-11 18:32:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-12 10:57:57 -0700
commitfe124c95df9e2acf202910b0510300e37afe074b (patch)
treeb212e742fa874a7a97104f8be695bbf5fe4364a6 /arch/ia64/mm
parentmm: mmu_notifier: fix and extend kerneldoc (diff)
downloadlinux-dev-fe124c95df9e2acf202910b0510300e37afe074b.tar.xz
linux-dev-fe124c95df9e2acf202910b0510300e37afe074b.zip
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 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup"). Commit 078eb6aa50dc ("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>
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