From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
linux-mm@kvack.org, Kyungmin Park <kyungmin.park@samsung.com>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Ankita Garg <ankita@in.ibm.com>,
Daniel Walker <dwalker@codeaurora.org>,
Johan MOSSBERG <johan.xx.mossberg@stericsson.com>,
Mel Gorman <mel@csn.ul.ie>, Pawel Osciak <pawel@osciak.com>
Subject: Re: [PATCH 04/12] mm: alloc_contig_freed_pages() added
Date: Fri, 01 Apr 2011 07:03:16 -0700 [thread overview]
Message-ID: <1301666596.30870.176.camel@nimitz> (raw)
In-Reply-To: <op.vs8cf5xd3l0zgt@mnazarewicz-glaptop>
On Fri, 2011-04-01 at 00:51 +0200, Michal Nazarewicz wrote:
> On Fri, 01 Apr 2011 00:26:51 +0200, Dave Hansen <dave@linux.vnet.ibm.com>
> wrote:
> >> Bug in the above place does not mean that we could not allocate
> >> memory. It means caller is broken.
> >
> > Could you explain that a bit?
> >
> > Is this a case where a device is mapped to a very *specific* range of
> > physical memory and no where else? What are the reasons for not marking
> > it off limits at boot? I also saw some bits of isolation and migration
> > in those patches. Can't the migration fail?
>
> The function is called from alloc_contig_range() (see patch 05/12) which
> makes sure that the PFN is valid. Situation where there is not enough
> space is caught earlier in alloc_contig_range().
>
> alloc_contig_freed_pages() must be given a valid PFN range such that all
> the pages in that range are free (as in are within the region tracked by
> page allocator) and of MIGRATETYPE_ISOLATE so that page allocator won't
> touch them.
OK, so it really is a low-level function only. How about a comment that
explicitly says this? "Only called from $FOO with the area already
isolated." It probably also deserves an __ prefix.
> That's why invalid PFN is a bug in the caller and not an exception that
> has to be handled.
>
> Also, the function is not called during boot time. It is called while
> system is already running.
What kind of success have you had running this in practice? I'd be
worried that some silly task or a sticky dentry would end up in the
range that you want to allocate in.
-- Dave
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WARNING: multiple messages have this Message-ID (diff)
From: dave@linux.vnet.ibm.com (Dave Hansen)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 04/12] mm: alloc_contig_freed_pages() added
Date: Fri, 01 Apr 2011 07:03:16 -0700 [thread overview]
Message-ID: <1301666596.30870.176.camel@nimitz> (raw)
In-Reply-To: <op.vs8cf5xd3l0zgt@mnazarewicz-glaptop>
On Fri, 2011-04-01 at 00:51 +0200, Michal Nazarewicz wrote:
> On Fri, 01 Apr 2011 00:26:51 +0200, Dave Hansen <dave@linux.vnet.ibm.com>
> wrote:
> >> Bug in the above place does not mean that we could not allocate
> >> memory. It means caller is broken.
> >
> > Could you explain that a bit?
> >
> > Is this a case where a device is mapped to a very *specific* range of
> > physical memory and no where else? What are the reasons for not marking
> > it off limits at boot? I also saw some bits of isolation and migration
> > in those patches. Can't the migration fail?
>
> The function is called from alloc_contig_range() (see patch 05/12) which
> makes sure that the PFN is valid. Situation where there is not enough
> space is caught earlier in alloc_contig_range().
>
> alloc_contig_freed_pages() must be given a valid PFN range such that all
> the pages in that range are free (as in are within the region tracked by
> page allocator) and of MIGRATETYPE_ISOLATE so that page allocator won't
> touch them.
OK, so it really is a low-level function only. How about a comment that
explicitly says this? "Only called from $FOO with the area already
isolated." It probably also deserves an __ prefix.
> That's why invalid PFN is a bug in the caller and not an exception that
> has to be handled.
>
> Also, the function is not called during boot time. It is called while
> system is already running.
What kind of success have you had running this in practice? I'd be
worried that some silly task or a sticky dentry would end up in the
range that you want to allocate in.
-- Dave
WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
linux-mm@kvack.org, Kyungmin Park <kyungmin.park@samsung.com>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Ankita Garg <ankita@in.ibm.com>,
Daniel Walker <dwalker@codeaurora.org>,
Johan MOSSBERG <johan.xx.mossberg@stericsson.com>,
Mel Gorman <mel@csn.ul.ie>, Pawel Osciak <pawel@osciak.com>
Subject: Re: [PATCH 04/12] mm: alloc_contig_freed_pages() added
Date: Fri, 01 Apr 2011 07:03:16 -0700 [thread overview]
Message-ID: <1301666596.30870.176.camel@nimitz> (raw)
In-Reply-To: <op.vs8cf5xd3l0zgt@mnazarewicz-glaptop>
On Fri, 2011-04-01 at 00:51 +0200, Michal Nazarewicz wrote:
> On Fri, 01 Apr 2011 00:26:51 +0200, Dave Hansen <dave@linux.vnet.ibm.com>
> wrote:
> >> Bug in the above place does not mean that we could not allocate
> >> memory. It means caller is broken.
> >
> > Could you explain that a bit?
> >
> > Is this a case where a device is mapped to a very *specific* range of
> > physical memory and no where else? What are the reasons for not marking
> > it off limits at boot? I also saw some bits of isolation and migration
> > in those patches. Can't the migration fail?
>
> The function is called from alloc_contig_range() (see patch 05/12) which
> makes sure that the PFN is valid. Situation where there is not enough
> space is caught earlier in alloc_contig_range().
>
> alloc_contig_freed_pages() must be given a valid PFN range such that all
> the pages in that range are free (as in are within the region tracked by
> page allocator) and of MIGRATETYPE_ISOLATE so that page allocator won't
> touch them.
OK, so it really is a low-level function only. How about a comment that
explicitly says this? "Only called from $FOO with the area already
isolated." It probably also deserves an __ prefix.
> That's why invalid PFN is a bug in the caller and not an exception that
> has to be handled.
>
> Also, the function is not called during boot time. It is called while
> system is already running.
What kind of success have you had running this in practice? I'd be
worried that some silly task or a sticky dentry would end up in the
range that you want to allocate in.
-- Dave
next prev parent reply other threads:[~2011-04-01 14:03 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-31 13:15 [PATCHv9 0/12] Contiguous Memory Allocator Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:15 ` [PATCH 01/12] lib: bitmap: Added alignment offset for bitmap_find_next_zero_area() Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:15 ` [PATCH 02/12] lib: genalloc: Generic allocator improvements Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:15 ` [PATCH 03/12] mm: move some functions from memory_hotplug.c to page_isolation.c Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:15 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 04/12] mm: alloc_contig_freed_pages() added Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 15:58 ` Dave Hansen
2011-03-31 15:58 ` Dave Hansen
2011-03-31 15:58 ` Dave Hansen
2011-03-31 19:24 ` Steven Rostedt
2011-03-31 19:24 ` Steven Rostedt
2011-03-31 19:24 ` Steven Rostedt
2011-03-31 20:33 ` Dave Hansen
2011-03-31 20:33 ` Dave Hansen
2011-03-31 20:33 ` Dave Hansen
2011-03-31 21:09 ` Michal Nazarewicz
2011-03-31 21:09 ` Michal Nazarewicz
2011-03-31 21:09 ` Michal Nazarewicz
2011-03-31 21:14 ` Dave Hansen
2011-03-31 21:14 ` Dave Hansen
2011-03-31 21:14 ` Dave Hansen
2011-03-31 22:18 ` Michal Nazarewicz
2011-03-31 22:18 ` Michal Nazarewicz
2011-03-31 22:18 ` Michal Nazarewicz
2011-03-31 22:26 ` Dave Hansen
2011-03-31 22:26 ` Dave Hansen
2011-03-31 22:26 ` Dave Hansen
2011-03-31 22:51 ` Michal Nazarewicz
2011-03-31 22:51 ` Michal Nazarewicz
2011-03-31 22:51 ` Michal Nazarewicz
2011-04-01 14:03 ` Dave Hansen [this message]
2011-04-01 14:03 ` Dave Hansen
2011-04-01 14:03 ` Dave Hansen
2011-04-04 13:15 ` Michal Nazarewicz
2011-04-04 13:15 ` Michal Nazarewicz
2011-04-04 13:15 ` Michal Nazarewicz
2011-04-05 7:23 ` Marek Szyprowski
2011-04-05 7:23 ` Marek Szyprowski
2011-04-05 7:23 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 05/12] mm: alloc_contig_range() added Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 16:02 ` Dave Hansen
2011-03-31 16:02 ` Dave Hansen
2011-03-31 16:02 ` Dave Hansen
2011-03-31 16:26 ` Michal Nazarewicz
2011-03-31 16:26 ` Michal Nazarewicz
2011-03-31 16:26 ` Michal Nazarewicz
2011-03-31 19:28 ` Steven Rostedt
2011-03-31 19:28 ` Steven Rostedt
2011-03-31 19:28 ` Steven Rostedt
2011-03-31 19:52 ` Michal Nazarewicz
2011-03-31 19:52 ` Michal Nazarewicz
2011-03-31 19:52 ` Michal Nazarewicz
2011-03-31 20:28 ` Dave Hansen
2011-03-31 20:28 ` Dave Hansen
2011-03-31 20:28 ` Dave Hansen
2011-03-31 21:17 ` Michal Nazarewicz
2011-03-31 21:17 ` Michal Nazarewicz
2011-03-31 21:17 ` Michal Nazarewicz
2011-03-31 19:26 ` Steven Rostedt
2011-03-31 19:26 ` Steven Rostedt
2011-03-31 19:26 ` Steven Rostedt
2011-03-31 16:04 ` Dave Hansen
2011-03-31 16:04 ` Dave Hansen
2011-03-31 16:04 ` Dave Hansen
2011-03-31 13:16 ` [PATCH 06/12] mm: cma: Contiguous Memory Allocator added Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 07/12] mm: MIGRATE_CMA migration type added Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 08/12] mm: MIGRATE_CMA isolation functions added Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 09/12] mm: MIGRATE_CMA support added to CMA Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 10/12] mm: cma: add CMA 'regions style' API (for testing) Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 11/12] v4l: videobuf2: add CMA allocator " Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` [PATCH 12/12] ARM: S5PC110: Added CMA regions to Aquila and Goni boards Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
2011-03-31 13:16 ` Marek Szyprowski
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