From: "Stephen C. Tweedie" <sct@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Stephen Tweedie <sct@redhat.com>
Subject: Re: [RFC] On paging of kernel VM.
Date: Mon, 9 Sep 2002 12:13:48 +0100 [thread overview]
Message-ID: <20020909121348.B4855@redhat.com> (raw)
In-Reply-To: <2653.1031563253@redhat.com>; from dwmw2@infradead.org on Mon, Sep 09, 2002 at 10:20:53AM +0100
Hi,
On Mon, Sep 09, 2002 at 10:20:53AM +0100, David Woodhouse wrote:
> I think I'd like to introduce 'real' VMAs into kernel space, so that areas
> in the vmalloc range can have 'real' vm_ops and more to the point a real
> nopage function.
The alternative is a kmap-style mechanism for temporarily mapping
pages beyond physical memory on demand. That would avoid the space
limits we have on vmalloc etc; there's only a few tens of MB of
address space we can use for mmap tricks in kernel space, so
persistent maps are seriously constrained if you've got a lot of flash
you want to map.
And with a kmap interface, your locking problems are much simpler ---
you can trap accesses at source and you don't have to go hunting ptes
to invalidate.
Cheers,
Stephen
WARNING: multiple messages have this Message-ID (diff)
From: "Stephen C. Tweedie" <sct@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Stephen Tweedie <sct@redhat.com>
Subject: Re: [RFC] On paging of kernel VM.
Date: Mon, 9 Sep 2002 12:13:48 +0100 [thread overview]
Message-ID: <20020909121348.B4855@redhat.com> (raw)
In-Reply-To: <2653.1031563253@redhat.com>; from dwmw2@infradead.org on Mon, Sep 09, 2002 at 10:20:53AM +0100
Hi,
On Mon, Sep 09, 2002 at 10:20:53AM +0100, David Woodhouse wrote:
> I think I'd like to introduce 'real' VMAs into kernel space, so that areas
> in the vmalloc range can have 'real' vm_ops and more to the point a real
> nopage function.
The alternative is a kmap-style mechanism for temporarily mapping
pages beyond physical memory on demand. That would avoid the space
limits we have on vmalloc etc; there's only a few tens of MB of
address space we can use for mmap tricks in kernel space, so
persistent maps are seriously constrained if you've got a lot of flash
you want to map.
And with a kmap interface, your locking problems are much simpler ---
you can trap accesses at source and you don't have to go hunting ptes
to invalidate.
Cheers,
Stephen
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next prev parent reply other threads:[~2002-09-09 11:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-09 9:20 [RFC] On paging of kernel VM David Woodhouse
2002-09-09 9:20 ` David Woodhouse
2002-09-09 11:13 ` Stephen C. Tweedie [this message]
2002-09-09 11:13 ` Stephen C. Tweedie
2002-09-09 11:24 ` David Woodhouse
2002-09-09 11:24 ` David Woodhouse
2002-09-10 0:28 ` Daniel Phillips
2002-09-10 0:28 ` Daniel Phillips
2002-09-10 6:08 ` David Woodhouse
2002-09-10 6:08 ` David Woodhouse
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