From: Michel Lespinasse <walken@google.com>
To: Jack Steiner <steiner@sgi.com>
Cc: linux-mm@kvack.org, mingo@elte.hu, linux-ia64@vger.kernel.org
Subject: Re: Very large memory configurations: > 16 TB
Date: Fri, 7 Jan 2011 04:16:49 -0800 [thread overview]
Message-ID: <AANLkTik_cTS629Ag+jmkJV+M6auEnu0r17EGZ8nXXBj1@mail.gmail.com> (raw)
In-Reply-To: <20110106170942.GA8253@sgi.com>
On Thu, Jan 6, 2011 at 9:09 AM, Jack Steiner <steiner@sgi.com> wrote:
> SGI is currently developing an x86_64 system with more than 16TB of memory per
> SSI. As far as I can tell, this should be supported. The relevant definitions
> such as MAX_PHYSMEM_BITS appear ok.
>
> One area of concern is page counts. Exceeding 16TB will also exceed MAX_INT
> page frames. The kernel (at least in all places I've found) keep pagecounts
> in longs.
>
> Have I missed anything? Should this > 16TB work? Are there any kernel problems or
> problems with user tools that anyone knows of.
>
> Any help or pointers to potential problem areas would be appreciated...
I don't know of any place that uses ints to count physical pages.
However, the page_referenced functions in mm/rmap.c return reference
counts as an integer. I believe a wraparound would only mislead the
LRU algorithms, but I haven't thought about it much. (Not sure why we
return a count anyway, since I believe callers only want to compare it
against zero ???)
--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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next prev parent reply other threads:[~2011-01-07 12:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-06 17:09 Jack Steiner
2011-01-07 12:16 ` Michel Lespinasse [this message]
2011-01-07 12:51 ` Ingo Molnar
2011-01-07 16:31 ` Christoph Lameter
2011-01-07 16:56 ` Ingo Molnar
2011-01-07 17:14 ` Christoph Lameter
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