* Re: [RFC PATCH 00/12] x86/mm: Implement lockless pgd_alloc()/pgd_free()
[not found] <1434031637-9091-1-git-send-email-mingo@kernel.org>
@ 2015-06-11 14:13 ` Ingo Molnar
0 siblings, 0 replies; only message in thread
From: Ingo Molnar @ 2015-06-11 14:13 UTC (permalink / raw)
To: linux-kernel, linux-mm
Cc: Andy Lutomirski, Andrew Morton, Denys Vlasenko, Brian Gerst,
Peter Zijlstra, Borislav Petkov, H. Peter Anvin, Linus Torvalds,
Oleg Nesterov, Thomas Gleixner, Waiman Long
[ I fat-fingered the linux-mm Cc:, so every reply will bounce on that,
sorry about that :-/ Fixed it in this mail's Cc: list. ]
* Ingo Molnar <mingo@kernel.org> wrote:
> Waiman Long reported 'pgd_lock' contention on high CPU count systems and
> proposed moving pgd_lock on a separate cacheline to eliminate false sharing and
> to reduce some of the lock bouncing overhead.
So 'pgd_lock' is a global lock, used for every new task creation:
arch/x86/mm/fault.c:DEFINE_SPINLOCK(pgd_lock);
which with a sufficiently high CPU count starts to hurt.
Thanks,
Ingo
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2015-06-11 14:13 ` [RFC PATCH 00/12] x86/mm: Implement lockless pgd_alloc()/pgd_free() Ingo Molnar
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