Re: [PATH V2 1/6] mm: Introduce a general RCU get_user_pages_fast.

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From: Will Deacon <will.deacon@arm.com>
To: Steve Capper <steve.capper@linaro.org>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"gary.robertson@linaro.org" <gary.robertson@linaro.org>,
	"christoffer.dall@linaro.org" <christoffer.dall@linaro.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"anders.roxell@linaro.org" <anders.roxell@linaro.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"dann.frazier@canonical.com" <dann.frazier@canonical.com>,
	Mark Rutland <Mark.Rutland@arm.com>,
	"mgorman@suse.de" <mgorman@suse.de>
Subject: Re: [PATH V2 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Wed, 27 Aug 2014 14:14:45 +0100	[thread overview]
Message-ID: <20140827131445.GB17601@arm.com> (raw)
In-Reply-To: <20140827125027.GA7765@linaro.org>

On Wed, Aug 27, 2014 at 01:50:28PM +0100, Steve Capper wrote:
> On Wed, Aug 27, 2014 at 09:54:42AM +0100, Will Deacon wrote:
> > On Thu, Aug 21, 2014 at 04:43:27PM +0100, Steve Capper wrote:
> > > @@ -672,3 +676,277 @@ struct page *get_dump_page(unsigned long addr)
> > >  	return page;
> > >  }
> > >  #endif /* CONFIG_ELF_CORE */
> > > +
> > > +#ifdef CONFIG_HAVE_RCU_GUP
> > > +
> > > +#ifdef __HAVE_ARCH_PTE_SPECIAL
> > 
> > Do we actually require this (pte special) if hugepages are disabled or
> > not supported?
> 
> We need this logic if we want use fast_gup on normal pages safely. The special
> bit indicates that we should not attempt to take a reference to the underlying
> page.
> 
> Huge pages are guaranteed not to be special.

Gah, I somehow mixed up sp-litting and sp-ecial. Step away from the
computer.

In which case, the patch looks fine. You might need to repost with '[PATCH]'
instead of '[PATH]', in case you confused people's filters.

Will

WARNING: multiple messages have this Message-ID (diff)

From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATH V2 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Wed, 27 Aug 2014 14:14:45 +0100	[thread overview]
Message-ID: <20140827131445.GB17601@arm.com> (raw)
In-Reply-To: <20140827125027.GA7765@linaro.org>

On Wed, Aug 27, 2014 at 01:50:28PM +0100, Steve Capper wrote:
> On Wed, Aug 27, 2014 at 09:54:42AM +0100, Will Deacon wrote:
> > On Thu, Aug 21, 2014 at 04:43:27PM +0100, Steve Capper wrote:
> > > @@ -672,3 +676,277 @@ struct page *get_dump_page(unsigned long addr)
> > >  	return page;
> > >  }
> > >  #endif /* CONFIG_ELF_CORE */
> > > +
> > > +#ifdef CONFIG_HAVE_RCU_GUP
> > > +
> > > +#ifdef __HAVE_ARCH_PTE_SPECIAL
> > 
> > Do we actually require this (pte special) if hugepages are disabled or
> > not supported?
> 
> We need this logic if we want use fast_gup on normal pages safely. The special
> bit indicates that we should not attempt to take a reference to the underlying
> page.
> 
> Huge pages are guaranteed not to be special.

Gah, I somehow mixed up sp-litting and sp-ecial. Step away from the
computer.

In which case, the patch looks fine. You might need to repost with '[PATCH]'
instead of '[PATH]', in case you confused people's filters.

Will

WARNING: multiple messages have this Message-ID (diff)

From: Will Deacon <will.deacon@arm.com>
To: Steve Capper <steve.capper@linaro.org>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"gary.robertson@linaro.org" <gary.robertson@linaro.org>,
	"christoffer.dall@linaro.org" <christoffer.dall@linaro.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"anders.roxell@linaro.org" <anders.roxell@linaro.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"dann.frazier@canonical.com" <dann.frazier@canonical.com>,
	Mark Rutland <Mark.Rutland@arm.com>,
	"mgorman@suse.de" <mgorman@suse.de>
Subject: Re: [PATH V2 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Wed, 27 Aug 2014 14:14:45 +0100	[thread overview]
Message-ID: <20140827131445.GB17601@arm.com> (raw)
In-Reply-To: <20140827125027.GA7765@linaro.org>

On Wed, Aug 27, 2014 at 01:50:28PM +0100, Steve Capper wrote:
> On Wed, Aug 27, 2014 at 09:54:42AM +0100, Will Deacon wrote:
> > On Thu, Aug 21, 2014 at 04:43:27PM +0100, Steve Capper wrote:
> > > @@ -672,3 +676,277 @@ struct page *get_dump_page(unsigned long addr)
> > >  	return page;
> > >  }
> > >  #endif /* CONFIG_ELF_CORE */
> > > +
> > > +#ifdef CONFIG_HAVE_RCU_GUP
> > > +
> > > +#ifdef __HAVE_ARCH_PTE_SPECIAL
> > 
> > Do we actually require this (pte special) if hugepages are disabled or
> > not supported?
> 
> We need this logic if we want use fast_gup on normal pages safely. The special
> bit indicates that we should not attempt to take a reference to the underlying
> page.
> 
> Huge pages are guaranteed not to be special.

Gah, I somehow mixed up sp-litting and sp-ecial. Step away from the
computer.

In which case, the patch looks fine. You might need to repost with '[PATCH]'
instead of '[PATH]', in case you confused people's filters.

Will

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next prev parent reply	other threads:[~2014-08-27 13:14 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-21 15:43 [PATH V2 0/6] RCU get_user_pages_fast and __get_user_pages_fast Steve Capper
2014-08-21 15:43 ` Steve Capper
2014-08-21 15:43 ` Steve Capper
2014-08-21 15:43 ` [PATH V2 1/6] mm: Introduce a general RCU get_user_pages_fast Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-27  8:54   ` Will Deacon
2014-08-27  8:54     ` Will Deacon
2014-08-27  8:54     ` Will Deacon
2014-08-27 12:50     ` Steve Capper
2014-08-27 12:50       ` Steve Capper
2014-08-27 12:50       ` Steve Capper
2014-08-27 13:14       ` Will Deacon [this message]
2014-08-27 13:14         ` Will Deacon
2014-08-27 13:14         ` Will Deacon
2014-08-27 14:28   ` Catalin Marinas
2014-08-27 14:28     ` Catalin Marinas
2014-08-27 14:28     ` Catalin Marinas
2014-08-27 14:42     ` Steve Capper
2014-08-27 14:42       ` Steve Capper
2014-08-27 14:42       ` Steve Capper
2014-08-27 15:01   ` Russell King - ARM Linux
2014-08-27 15:01     ` Russell King - ARM Linux
2014-08-27 15:01     ` Russell King - ARM Linux
2014-08-28  8:59     ` Steve Capper
2014-08-28  8:59       ` Steve Capper
2014-08-28  8:59       ` Steve Capper
2014-08-21 15:43 ` [PATH V2 2/6] arm: mm: Introduce special ptes for LPAE Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-27 10:46   ` Catalin Marinas
2014-08-27 10:46     ` Catalin Marinas
2014-08-27 10:46     ` Catalin Marinas
2014-08-27 12:52     ` Steve Capper
2014-08-27 12:52       ` Steve Capper
2014-08-27 12:52       ` Steve Capper
2014-08-21 15:43 ` [PATH V2 3/6] arm: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-27 11:50   ` Catalin Marinas
2014-08-27 11:50     ` Catalin Marinas
2014-08-27 11:50     ` Catalin Marinas
2014-08-27 12:59     ` Steve Capper
2014-08-27 12:59       ` Steve Capper
2014-08-27 12:59       ` Steve Capper
2014-08-21 15:43 ` [PATH V2 4/6] arm: mm: Enable RCU fast_gup Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-27 11:51   ` Catalin Marinas
2014-08-27 11:51     ` Catalin Marinas
2014-08-27 11:51     ` Catalin Marinas
2014-08-27 13:01     ` Steve Capper
2014-08-27 13:01       ` Steve Capper
2014-08-27 13:01       ` Steve Capper
2014-08-21 15:43 ` [PATH V2 5/6] arm64: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-27 10:48   ` Catalin Marinas
2014-08-27 10:48     ` Catalin Marinas
2014-08-27 10:48     ` Catalin Marinas
2014-08-27 13:08     ` Steve Capper
2014-08-27 13:08       ` Steve Capper
2014-08-27 13:08       ` Steve Capper
2014-08-21 15:43 ` [PATH V2 6/6] arm64: mm: Enable RCU fast_gup Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-21 15:43   ` Steve Capper
2014-08-27 11:09   ` Catalin Marinas
2014-08-27 11:09     ` Catalin Marinas
2014-08-27 11:09     ` Catalin Marinas
2014-08-27 13:43     ` Steve Capper
2014-08-27 13:43       ` Steve Capper
2014-08-27 13:43       ` Steve Capper
2014-08-21 20:42 ` [PATH V2 0/6] RCU get_user_pages_fast and __get_user_pages_fast Dann Frazier
2014-08-21 20:42   ` Dann Frazier
2014-08-21 20:42   ` Dann Frazier
2014-08-22  8:11   ` Steve Capper
2014-08-22  8:11     ` Steve Capper
2014-08-22  8:11     ` Steve Capper

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