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From: Peter Zijlstra <peterz@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	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
Subject: Re: [PATCHv4 09/10] mm: implement split page table lock for PMD level
Date: Fri, 4 Oct 2013 09:21:32 +0200	[thread overview]
Message-ID: <20131004072132.GT28601@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20131003161109.aa568784d6fc48e61dc1d33e@linux-foundation.org>

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@linux.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.

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	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
Subject: Re: [PATCHv4 09/10] mm: implement split page table lock for PMD level
Date: Fri, 4 Oct 2013 09:21:32 +0200	[thread overview]
Message-ID: <20131004072132.GT28601@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20131003161109.aa568784d6fc48e61dc1d33e@linux-foundation.org>

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@linux.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.

--
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  parent reply	other threads:[~2013-10-04  7:21 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-27 13:16 [PATCHv4 00/10] split page table lock for PMD tables Kirill A. Shutemov
2013-09-27 13:16 ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 01/10] mm: rename USE_SPLIT_PTLOCKS to USE_SPLIT_PTE_PTLOCKS Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 02/10] mm: convert mm->nr_ptes to atomic_t Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 20:46   ` Cody P Schafer
2013-09-27 20:46     ` Cody P Schafer
2013-09-27 21:01     ` Dave Hansen
2013-09-27 21:01       ` Dave Hansen
2013-09-27 22:24     ` Kirill A. Shutemov
2013-09-28  0:13       ` Johannes Weiner
2013-09-28  0:13         ` Johannes Weiner
2013-09-28 16:12         ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 03/10] mm: introduce api for split page table lock for PMD level Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 04/10] mm, thp: change pmd_trans_huge_lock() to return taken lock Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 05/10] mm, thp: move ptl taking inside page_check_address_pmd() Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 06/10] mm, thp: do not access mm->pmd_huge_pte directly Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 07/10] mm, hugetlb: convert hugetlbfs to use split pmd lock Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 08/10] mm: convent the rest to new page table lock api Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 09/10] mm: implement split page table lock for PMD level Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-10-03 23:11   ` Andrew Morton
2013-10-03 23:11     ` Andrew Morton
2013-10-03 23:38     ` Kirill A. Shutemov
2013-10-03 23:38       ` Kirill A. Shutemov
2013-10-04  0:34       ` Kirill A. Shutemov
2013-10-04  7:21     ` Peter Zijlstra [this message]
2013-10-04  7:21       ` Peter Zijlstra
2013-10-03 23:42   ` Kirill A. Shutemov
2013-09-27 13:16 ` [PATCHv4 10/10] x86, mm: enable " Kirill A. Shutemov
2013-09-27 13:16   ` Kirill A. Shutemov
2013-10-04 20:12 ` [PATCHv4 00/10] split page table lock for PMD tables Alex Thorlton
2013-10-04 20:12   ` Alex Thorlton
2013-10-04 20:26   ` Kirill A. Shutemov
2013-10-04 20:26     ` Kirill A. Shutemov
2013-10-04 20:31     ` Alex Thorlton
2013-10-04 20:31       ` Alex Thorlton
2013-10-07  9:48       ` Kirill A. Shutemov
2013-10-07  9:48         ` Kirill A. Shutemov
2013-10-08 21:47         ` Alex Thorlton
2013-10-08 21:47           ` Alex Thorlton

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