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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
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Subject: Re: [PATCHv5 00/11] split page table lock for PMD tables
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Date: Tue,  8 Oct 2013 12:50:06 +0300 (EEST)
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To: Ingo Molnar <mingo@kernel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, Alex Thorlton <athorlton@sgi.com>, Ingo Molnar <mingo@redhat.com>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, "Eric W . Biederman" <ebiederm@xmission.com>, "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>, Al Viro <viro@zeniv.linux.org.uk>, Andi Kleen <ak@linux.intel.com>, Andrea Arcangeli <aarcange@redhat.com>, Dave Hansen <dave.hansen@intel.com>, Dave Jones <davej@redhat.com>, David Howells <dhowells@redhat.com>, Frederic Weisbecker <fweisbec@gmail.com>, Johannes Weiner <hannes@cmpxchg.org>, Kees Cook <keescook@chromium.org>, Mel Gorman <mgorman@suse.de>, Michael Kerrisk <mtk.manpages@gmail.com>, Oleg Nesterov <oleg@redhat.com>, Rik van Riel <riel@redhat.com>, Robin Holt <robinmholt@gmail.com>, Sedat Dilek <sedat.dilek@gmail.com>, Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org, linux-mm@kvack.org

Ingo Molnar wrote:
> 
> * Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote:
> 
> > > What must arch maintainers do to enable it?  Have you any particular 
> > > suggestions, warnings etc to make their lives easier?
> > 
> > The last patch is a good illustration what need to be done. It's very 
> > straight forward, I don't see any pitfalls.
> 
> Might make sense to stick that somewhere into Documentation/mm/, to make 
> arch maintainers feel all warm and fuzzy if they look into enabling this 
> feature on their architecture.

I want to rework code around page->ptl a bit more:
 - allow pgtable_page_ctor() to fail and modify callers to handle it;
 - if sizeof(spinlock_t) > sizeof(long) allocate the spinlock_t
   dynamically.

It will allow to use split lock with DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC.
And it will make -rt guys happier. ;)

After that I'll document it. Does it work for you?

-- 
 Kirill A. Shutemov

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