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Date: Fri, 4 Oct 2013 09:21:32 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Andrew Morton <akpm@...ux-foundation.org> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Alex Thorlton <athorlton@....com>, Ingo Molnar <mingo@...hat.com>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, "Eric W . Biederman" <ebiederm@...ssion.com>, "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>, Al Viro <viro@...iv.linux.org.uk>, Andi Kleen <ak@...ux.intel.com>, Andrea Arcangeli <aarcange@...hat.com>, Dave Hansen <dave.hansen@...el.com>, Dave Jones <davej@...hat.com>, David Howells <dhowells@...hat.com>, Frederic Weisbecker <fweisbec@...il.com>, Johannes Weiner <hannes@...xchg.org>, Kees Cook <keescook@...omium.org>, Mel Gorman <mgorman@...e.de>, Michael Kerrisk <mtk.manpages@...il.com>, Oleg Nesterov <oleg@...hat.com>, Rik van Riel <riel@...hat.com>, Robin Holt <robinmholt@...il.com>, Sedat Dilek <sedat.dilek@...il.com>, Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCHv4 09/10] mm: implement split page table lock for PMD level On Thu, Oct 03, 2013 at 04:11:09PM -0700, Andrew Morton wrote: > On Fri, 27 Sep 2013 16:16:26 +0300 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote: > > > The basic idea is the same as with PTE level: the lock is embedded into > > struct page of table's page. > > > > We can't use mm->pmd_huge_pte to store pgtables for THP, since we don't > > take mm->page_table_lock anymore. Let's reuse page->lru of table's page > > for that. > > > > pgtable_pmd_page_ctor() returns true, if initialization is successful > > and false otherwise. Current implementation never fails, but assumption > > that constructor can fail will help to port it to -rt where spinlock_t > > is rather huge and cannot be embedded into struct page -- dynamic > > allocation is required. > > spinlock_t is rather large when lockdep is enabled. What happens? I could go fix all the arch code and pgtable ctor thingies and do the same thing we do on -rt if anybody cares. Hugh thought the single pagetable lock would catch the more interesting locking scenarios, but its of course sad to have an entire locking scheme not covered by lockdep -- that's just waiting for a bug to sneak in there. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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